Oral cholera vaccines (Shanchol, Euvichol, Dukoral, Vaxchora)

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disease risks

post-acute and long-term sequelae

vaccine efficacy and effectiveness

vaccine safety and adverse events

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Cholera Vibrio cholerae O1 and O139

Disease risks

Acute risks of the infection itself: complications, hospitalisation, ICU, death.

Outcome (O)	Population (P)	Estimate	Design (S)	Source
Cholera cases worldwide each year (researcher estimate) severity: any case definition: Estimated, not reported, cholera cases worldwide	all ages vaccination status: mixed country: worldwide setting: community period: current estimate as of the 2026 fact sheet All ages	1.3 to 4.0 million estimated cholera cases worldwide per year per year worldwide	expert body	who.int quote Researchers estimate that there are 1.3 to 4.0 million cases and 21 000 to 143 000 deaths from cholera worldwide each year (1) . Key facts A modelled estimate far above the figure countries report to WHO; the reported figure is a separate record.
Deaths from cholera worldwide each year (researcher estimate) severity: death case definition: Estimated, not reported, cholera deaths worldwide	all ages vaccination status: mixed country: worldwide setting: community period: current estimate as of the 2026 fact sheet All ages	21 000 to 143 000 estimated cholera deaths worldwide per year per year worldwide	expert body	who.int quote Researchers estimate that there are 1.3 to 4.0 million cases and 21 000 to 143 000 deaths from cholera worldwide each year (1) . Key facts An estimate with a sevenfold range, reflecting how little cholera mortality surveillance captures.
Case fatality in cholera treatment centres (programmatic target) severity: death case definition: Deaths among patients treated in cholera treatment centres	all ages vaccination status: mixed country: worldwide setting: cholera treatment centre period: current guidance All ages	below 1 CFR (%) target in treatment centres per treated case	expert body	who.int quote The case fatality rate in treatment centres should remain below 1%. Treatment A target, not a measured rate. It is the benchmark against which the Haiti and Yemen outbreak CFR records should be read.
Death from untreated cholera severity: death case definition: Untreated cholera	all ages vaccination status: not reported country: not specified setting: untreated period: current guidance All ages	50 CFR (%) untreated per case	expert body	cdc.gov quote The case-fatality ratio for untreated cholera can reach 50%, but with adequate and timely rehydration, the case-fatality ratio is <1%. Clinical presentation An upper bound for untreated disease stated by CDC, not an observed cohort figure. The same sentence gives the figure with timely rehydration, recorded separately.
Death from cholera with adequate and timely rehydration severity: death case definition: Cholera treated with adequate and timely rehydration	all ages vaccination status: not reported country: not specified setting: treated with rehydration period: current guidance All ages	<1 CFR (%) with timely rehydration per case	expert body	cdc.gov quote The case-fatality ratio for untreated cholera can reach 50%, but with adequate and timely rehydration, the case-fatality ratio is <1%. Clinical presentation The contrast with the untreated-cholera record is the central fact about cholera: most of its mortality is a treatment-access problem rather than an inevitable consequence of infection.
Severe cholera (cholera gravis) severity: severe case definition: Profuse watery diarrhoea with rapid severe volume depletion	all ages vaccination status: not reported country: not specified setting: community period: current guidance All ages	10 proportion of cholera episodes that are severe (%) per cholera episode	expert body	cdc.gov quote Severe cholera ( cholera gravis ) occurs in approximately 10% of cholera episodes and is characterized by profuse watery diarrhea, described as rice-water stools, often accompanied by nausea and vomiting that can rapidly lead to severe volume depletion. Clinical presentation Most infections are mild or asymptomatic; this is the fraction that becomes life-threatening without rapid fluid replacement.
Severe symptoms after cholera infection severity: severe case definition: Watery diarrhoea, vomiting and leg cramps	all ages vaccination status: not reported country: worldwide setting: community period: 2025 page All ages	1 in 10 proportion of infected people with severe symptoms per person who gets cholera	expert body	cdc.gov quote About 1 in 10 people develop severe symptoms such as watery diarrhea, vomiting, and leg cramps. Signs and symptoms CDC's plain-language version of the severe-case fraction; the Yellow Book states the same proportion as a percentage.
Cholera incidence over 5 years in unvaccinated residents of an endemic slum severity: medically attended case definition: Culture-confirmed Vibrio cholerae O1 diarrhoea severe enough to seek care at a health facility	non-pregnant individuals older than 1 year vaccination status: unvaccinated country: India setting: urban slum, endemic (Kolkata) period: 2006-2011 n: 34 968 placebo recipients 1-4y5-11y12-17y18-49y50-64y65+	6.3 cumulative cholera incidence per 1000 over 5 years per 1000 placebo recipients over 5 years	RCT	Bhattacharya et al. 2013 Lancet Infect Dis quote FINDINGS: 69 of 31 932 recipients of vaccine and 219 of 34 968 recipients of placebo developed cholera during 5 year follow-up (incidence 2·2 per 1000 in the vaccine group and 6·3 per 1000 in the placebo group). abstract, FINDINGS The placebo arm of the Kolkata trial, i.e. the untreated background risk of medically attended cholera in an endemic slum. Only medically attended, culture-confirmed episodes count, so true infection incidence was higher.
Cholera incidence in unvaccinated (placebo) residents by neighbourhood vaccine coverage severity: medically attended case definition: Cholera among placebo recipients during the first year of surveillance	children and adult women sex: children of both sexes and adult women vaccination status: unvaccinated country: Bangladesh setting: rural endemic (Matlab) period: first year of the 1985 trial 1-4y5-11y12-17y18-49y50-64y65+	7.01 cholera incidence per 1000 placebo recipients, lowest coverage quintile per 1000 placebo recipients in one year	RCT	Ali et al. 2005 Lancet quote Incidence rates of cholera among placebo recipients were inversely related to levels of vaccine coverage (7.01 cases per 1000 in the lowest quintile of coverage vs 1.47 cases per 1000 in the highest quintile; p<0.0001 for trend). abstract, FINDINGS The comparison figure of 1.47 per 1000 in the highest-coverage quintile is in the same sentence and is filed as the herd-protection efficacy record. This record is the risk run by an unvaccinated person in a barely vaccinated neighbourhood.
Cholera risk in people living close to a cholera case severity: medically attended case definition: Attack rate in rings of residents around an index case versus around a matched index control	residents of the study area of all ages vaccination status: mixed country: India setting: urban slum, endemic (Kolkata) period: 2006-2011 n: 144,106 individuals under surveillance All ages	5-11 relative risk of cholera, exposed versus non-exposed ring per resident of the ring	RCT	Ali et al. 2016 PLoS Med quote Cholera risk among the cohort exposed to cholera cases was 5-11 times higher than that among the cohort not exposed to cholera cases. abstract, METHODS AND FINDINGS A range across ring radii and time windows, not a single estimate with an interval. It is the rationale for ring vaccination: risk is concentrated in space and time around a case.
Cholera cases reported to WHO severity: any case definition: Cases reported to WHO by member states	all ages vaccination status: mixed country: 47 reporting countries setting: community period: 2025 All ages	451 499 cholera cases reported to WHO per year worldwide	surveillance	who.int quote In 2025, 47 countries reported 451 499 cases and 7870 deaths to WHO (3) . Epidemiology, risk factors and disease burden Reported cases, which WHO states are lower than the researcher-estimated burden. Not comparable with the modelled estimate recorded from the same fact sheet.
Deaths from cholera reported to WHO severity: death case definition: Deaths reported to WHO by member states	all ages vaccination status: mixed country: 47 reporting countries setting: community period: 2025 All ages	7870 cholera deaths reported to WHO per year worldwide	surveillance	who.int quote In 2025, 47 countries reported 451 499 cases and 7870 deaths to WHO (3) . Epidemiology, risk factors and disease burden WHO states this was the highest annual number of reported cholera deaths since the late nineteen-nineties.
Cholera attack rate during the Yemen epidemic severity: any case definition: Suspected cholera cases presenting at health facilities under national surveillance	all ages vaccination status: mixed country: Yemen setting: conflict-affected national outbreak period: Sept 28, 2016 to March 12, 2018 n: 1 103 683 suspected cases All ages	3.69 attack rate (%) per population of Yemen	surveillance	Camacho et al. 2018 Lancet Glob Health quote FINDINGS: From Sept 28, 2016, to March 12, 2018, 1 103 683 suspected cholera cases (attack rate 3·69%) and 2385 deaths (case fatality risk 0·22%) were reported countrywide. abstract, FINDINGS Suspected, largely unconfirmed cases in the largest documented cholera epidemic of modern times.
Death from cholera during the Yemen epidemic severity: death case definition: Deaths among reported suspected cholera cases	all ages vaccination status: mixed country: Yemen setting: conflict-affected national outbreak period: Sept 28, 2016 to March 12, 2018 n: 2385 deaths among 1 103 683 suspected cases All ages	0.22 CFR (%) per reported suspected case	surveillance	Camacho et al. 2018 Lancet Glob Health quote FINDINGS: From Sept 28, 2016, to March 12, 2018, 1 103 683 suspected cholera cases (attack rate 3·69%) and 2385 deaths (case fatality risk 0·22%) were reported countrywide. abstract, FINDINGS A low CFR despite the scale, achieved with mass oral rehydration; the denominator is suspected cases, which inflates the denominator relative to confirmed cholera.
Hospitalisation for cholera in the 2010 Haiti outbreak severity: hospitalisation case definition: Cases reported by the Haitian Ministry of Public Health and Population	all ages vaccination status: unvaccinated country: Haiti setting: national outbreak in a previously cholera-free country period: October to December 3, 2010 n: 91,770 reported cases All ages	47.1 proportion of reported cases hospitalised (%) per reported cholera case	surveillance	Centers 2010 MMWR Morb Mortal Wkly Rep quote As of December 3, MSPP reported 91,770 cases of cholera from all 10 departments and the capital city of Port-au-Prince; 43,243 (47.1%) patients had been hospitalized, and 2,071 (2.3%) had died. abstract Early epidemic figures in a population with no prior immunity and no vaccination; reporting was incomplete, and the same source notes deaths occurring within two hours of symptom onset.
Death from cholera in the 2010 Haiti outbreak severity: death case definition: Deaths among reported cases	all ages vaccination status: unvaccinated country: Haiti setting: national outbreak in a previously cholera-free country period: October to December 3, 2010 n: 2,071 deaths among 91,770 reported cases All ages	2.3 CFR (%) per reported cholera case	surveillance	Centers 2010 MMWR Morb Mortal Wkly Rep quote As of December 3, MSPP reported 91,770 cases of cholera from all 10 departments and the capital city of Port-au-Prince; 43,243 (47.1%) patients had been hospitalized, and 2,071 (2.3%) had died. abstract More than twice the 1% benchmark for treatment centres, in the opening weeks of an epidemic in a country with no previous cholera.
Death from cholera in remote rural districts severity: death case definition: Self-reported watery diarrhoea episodes and deaths in a household cluster survey	all ages vaccination status: unvaccinated country: Haiti setting: remote rural, poor road access period: outbreak 2010-2011, surveyed April-May 2011 n: 3,187 households and 16,900 individuals All ages	15.2 CFR (%) in the most remote districts per reported case in the survey	surveillance	Page et al. 2015 PLoS Negl Trop Dis quote The two more remote districts, Borgne and Pilate were most affected with attack rates up to 16.2%, and case fatality rates up to 15.2% as compared to the two more accessible districts. abstract, METHODOLOGY/PRINCIPAL FINDINGS A community survey, not facility surveillance: these deaths largely occurred without access to rehydration. It shows what the untreated CFR looks like in practice and should be read beside the national surveillance figure.
Cholera attack rate in remote rural districts severity: any case definition: Self-reported watery diarrhoea episodes in a household cluster survey	all ages vaccination status: unvaccinated country: Haiti setting: remote rural, poor road access period: outbreak 2010-2011, surveyed April-May 2011 n: 16,900 individuals surveyed All ages	16.2 attack rate (%) per person surveyed	surveillance	Page et al. 2015 PLoS Negl Trop Dis quote The two more remote districts, Borgne and Pilate were most affected with attack rates up to 16.2%, and case fatality rates up to 15.2% as compared to the two more accessible districts. abstract, METHODOLOGY/PRINCIPAL FINDINGS Attack rate of self-reported watery diarrhoea, not laboratory-confirmed cholera.
Any episode of watery diarrhoea during the epidemic severity: any case definition: Self-reported watery diarrhoea since the start of the outbreak	all ages vaccination status: unvaccinated country: Haiti setting: rural Nord department period: outbreak 2010-2011, surveyed April-May 2011 n: 16,900 individuals in 3,187 households All ages	12.0 proportion reporting watery diarrhoea (%) per person surveyed	surveillance	Page et al. 2015 PLoS Negl Trop Dis quote A total of 3,187 households and 16,900 individuals were included in the survey, of whom 2,034 (12.0%) reported at least one episode of watery diarrhea since the beginning of the outbreak. abstract, METHODOLOGY/PRINCIPAL FINDINGS Self-report over the whole epidemic period, so it includes non-cholera diarrhoea.
All-cause mortality during the first epidemic wave severity: death case definition: Deaths from any cause reported in retrospective household surveys	all ages vaccination status: unvaccinated country: Haiti setting: four sites in northern Haiti period: first wave of the 2010 epidemic n: 70,903 participants All ages	19.1-35.4 crude mortality per 1,000 person-years per 1,000 person-years	surveillance	Luquero et al. 2016 Emerg Infect Dis quote Overall, 70,903 participants were included; at all sites, the crude mortality rates (19.1-35.4 deaths/1,000 person-years) were higher than the expected baseline mortality rate for Haiti (9 deaths/1,000 person-years). abstract All-cause, not cholera-specific: the same sentence gives the expected baseline of 9 deaths per 1,000 person-years for Haiti, and the authors read the excess as cholera mortality under-reported by facility surveillance. Do not treat as a CFR.
Death from cholera in African surveillance sites severity: death case definition: Deaths among cholera cases in enhanced surveillance zones and outbreak sites	all ages vaccination status: mixed country: Togo, Democratic Republic of Congo, Guinea, Uganda, Mozambique, Cote d'Ivoire setting: LMIC surveillance zones and outbreak sites period: June 2011 to December 2013 n: 13,377 reported suspected cases All ages	1 (range 0-10) CFR (%) by country, median (range) per cholera case	surveillance	Sauvageot et al. 2016 PLoS Negl Trop Dis quote Case fatality ratios ranged from 0-10% (median, 1%) by country. abstract, METHODS/PRINCIPAL FINDINGS Median of country-level case fatality ratios with a wide range; the upper end is ten times the WHO treatment-centre benchmark.
Confirmed cholera incidence in a high-burden African city severity: any case definition: Culture-confirmed cases corrected for incomplete culture testing and imperfect test sensitivity	all ages vaccination status: mixed country: Democratic Republic of Congo (Goma) setting: urban endemic period: June 2011 to December 2013 All ages	20.2 corrected annual confirmed cholera incidence per 10,000 population per 10,000 population per year	surveillance	Sauvageot et al. 2016 PLoS Negl Trop Dis quote Goma and Conakry had corrected incidences of 20.2 and 5.8 respectively, while the other zones a median of 0.3. abstract, METHODS/PRINCIPAL FINDINGS Corrected, not raw, incidence; the same sentence gives 5.8 for Conakry and a median of 0.3 for the other surveillance zones, so the geographic spread is two orders of magnitude.
Share of suspected cholera cases in children under five severity: any case definition: Age of suspected cholera cases in surveillance zones and outbreak sites	children under five years, as a share of all suspected cases vaccination status: mixed country: six African countries setting: LMIC surveillance zones and outbreak sites period: June 2011 to December 2013 Infant <1y1-4y	0-40 proportion of suspected cases aged under five years (%) per suspected cholera case	surveillance	Sauvageot et al. 2016 PLoS Negl Trop Dis quote From 0-40% of suspected cases were aged under five years and from 0.3-86% had rice water stools. abstract, METHODS/PRINCIPAL FINDINGS A range across sites, not a single estimate: the share of cholera borne by young children varies enormously between African settings, which is why age-specific vaccine effectiveness matters differently in each.
Annual cholera cases in endemic countries severity: any case definition: Modelled cases from population-based incidence rates applied to at-risk populations	all ages vaccination status: mixed country: 51 cholera-endemic countries setting: LMIC, endemic period: 2008-2012 input data All ages	2.86 (1.3–4.0) estimated annual cholera cases (millions) per year in endemic countries	modelling	Ali et al. 2015 PLoS Negl Trop Dis quote An estimated 2.86 million cholera cases (uncertainty range: 1.3m-4.0m) occur annually in endemic countries. abstract, METHODS/PRINCIPAL FINDINGS An uncertainty range, not a confidence interval. This is the source the WHO fact sheet range traces back to.
Annual cholera deaths in endemic countries severity: death case definition: Cases multiplied by inverse variance-weighted average case-fatality rates from the literature	all ages vaccination status: mixed country: 51 cholera-endemic countries setting: LMIC, endemic period: 2008-2012 input data All ages	95,000 (21,000–143,000) estimated annual cholera deaths per year in endemic countries	modelling	Ali et al. 2015 PLoS Negl Trop Dis quote Among these cases, there are an estimated 95,000 deaths (uncertainty range: 21,000-143,000). abstract, METHODS/PRINCIPAL FINDINGS An uncertainty range, not a confidence interval. Sub-Saharan Africa accounts for most of this burden according to the same paper.
Population at risk of cholera in endemic countries severity: exposure risk case definition: Population without sustainable access to improved sanitation in countries modelled as endemic	all ages vaccination status: mixed country: cholera-endemic countries setting: LMIC, endemic period: 2008-2012 All ages	1.3 population at risk (billions) per population of endemic countries	modelling	Ali et al. 2015 PLoS Negl Trop Dis quote We found that approximately 1.3 billion people are at risk for cholera in endemic countries. abstract, METHODS/PRINCIPAL FINDINGS A denominator, not a risk: it is the size of the population from which the case and death estimates are drawn.
Reported suspected cholera incidence across Africa severity: any case definition: Reported suspected cholera from national surveillance, modelled on a 20-km grid	all ages vaccination status: mixed country: 43 African countries setting: LMIC, continental period: 2016-2020 All ages	11 mean annual incidence per 100,000 population per 100,000 population per year	modelling	Perez-Saez et al. 2025 Nat Med quote Across 43 countries, mean annual incidence rates remained at 11 cases per 100,000 population, with 125,701 cases estimated annually (95% credible interval (CrI): 124,737-126,717) from 2016 to 2020. abstract The same sentence gives 125,701 estimated cases annually with a credible interval; incidence shifted from western to eastern Africa over the two periods compared.
Estimated annual reported cholera cases in Africa severity: any case definition: Reported suspected cholera cases, modelled	all ages vaccination status: mixed country: 43 African countries setting: LMIC, continental period: 2016-2020 All ages	125,701 (124,737–126,717) estimated annual cholera cases in Africa per year across 43 countries	modelling	Perez-Saez et al. 2025 Nat Med quote Across 43 countries, mean annual incidence rates remained at 11 cases per 100,000 population, with 125,701 cases estimated annually (95% credible interval (CrI): 124,737-126,717) from 2016 to 2020. abstract A credible interval, not a confidence interval. This counts reported suspected cases, so it is far below the modelled true burden in the modelled global burden record.
Severe dehydration among hospitalised cholera patients severity: severe dehydration case definition: Inpatients with cholera at two hospitals	not reported by band; inpatients of all ages vaccination status: mixed country: Yemen setting: hospital, conflict-affected period: 3 February to 8 December 2017 n: 172 hospitalisations All ages	94.8 proportion of hospitalised cholera patients severely dehydrated (%) per cholera hospitalisation	case series	Alassar et al. 2020 Germs quote RESULTS: Preliminary findings from 172 hospitalizations for cholera during the study period include 163 that were severely dehydrated (94.8%). abstract, RESULTS Denominator is hospitalisations, not infections: these are the patients sick enough to be admitted, so this must not be read as the proportion of infected people who become severely dehydrated. Preliminary findings in a cohort profile.

Vaccine efficacy and effectiveness

Every estimate compiled, annotated by population (P), intervention (I), comparator (C), outcome (O) and study design (S).

Outcome (O)	Population (P)	Intervention / comparator	Estimate	Design (S)	Source
Cases of cholera severity: any case definition: Cholera cases as defined in the included randomised trials	general population of children and adults, plus an adult male population country: Bangladesh and Peru setting: endemic rural and military period: trials from 1985 onwards n: 16,423 participants 1-4y5-11y12-17y18-49y50-64y65+	whole-cell plus recombinant B subunit vaccine (WC-rBS, Dukoral) platform: killed whole-cell with recombinant B subunit doses: 2 doses with or without a booster vs placebo, another vaccine, or no vaccine	76 (0.08–0.65 RR CI) VE (%)	systematic review GRADE: high 2 trials	Saif-Ur-Rahman et al. 2024 Cochrane Database Syst Rev quote Two doses of Dukoral with or without a booster dose reduces cases of cholera at two-year follow-up in a general population of children and adults, and at five-month follow-up in an adult male population (overall VE 76%; RR 0.24, 95% confidence interval (CI) 0.08 to 0.65; 2 trials, 16,423 participants; high-certainty evidence). abstract, MAIN RESULTS The confidence interval is reported on the risk-ratio scale (RR 0.24, 95% CI 0.08 to 0.65), not as percentages. Two heterogeneous trials are pooled here: a two-year follow-up in a general population and a five-month follow-up in adult men.
Cases of cholera at one-year follow-up severity: any case definition: Cholera cases as defined in the included randomised trials	children and adults aged 1 year and older country: India and Bangladesh setting: urban endemic period: trials from 2006 onwards n: 241,631 participants 1-4y5-11y12-17y18-49y50-64y65+	bivalent whole-cell vaccine (BivWC, Shanchol) platform: killed whole-cell doses: 2 time since vaccination: 1 year vs placebo, another vaccine, or no vaccine	37 (0.47–0.85 RR CI) VE (%)	systematic review GRADE: high 2 trials	Saif-Ur-Rahman et al. 2024 Cochrane Database Syst Rev quote Two doses of Shanchol reduces cases of cholera at one-year follow-up (overall VE 37%; RR 0.63, 95% CI 0.47 to 0.85; 2 trials, 241,631 participants; high-certainty evidence), at two-year follow-up (overall VE 64%; RR 0.36, 95% CI 0.16 to 0.81; 2 trials, 168,540 participants; moderate-certainty evidence), and at five-year follow-up (overall VE 80%; RR 0.20, 95% CI 0.15 to 0.26; 1 trial, 54,519 participants; high-certainty evidence). abstract, MAIN RESULTS Interval on the RR scale (RR 0.63, 95% CI 0.47 to 0.85). Cochrane's one-year pooled figure is markedly lower than the individual Kolkata trial's cumulative estimate because it pools the Dhaka programme-delivery trial, which measured total effectiveness at partial coverage.
Cases of cholera at two-year follow-up severity: any case definition: Cholera cases as defined in the included randomised trials	children and adults aged 1 year and older country: India and Bangladesh setting: urban endemic period: trials from 2006 onwards n: 168,540 participants 1-4y5-11y12-17y18-49y50-64y65+	bivalent whole-cell vaccine (BivWC, Shanchol) platform: killed whole-cell doses: 2 time since vaccination: 2 years vs placebo, another vaccine, or no vaccine	64 (0.16–0.81 RR CI) VE (%)	systematic review GRADE: moderate 2 trials	Saif-Ur-Rahman et al. 2024 Cochrane Database Syst Rev quote Two doses of Shanchol reduces cases of cholera at one-year follow-up (overall VE 37%; RR 0.63, 95% CI 0.47 to 0.85; 2 trials, 241,631 participants; high-certainty evidence), at two-year follow-up (overall VE 64%; RR 0.36, 95% CI 0.16 to 0.81; 2 trials, 168,540 participants; moderate-certainty evidence), and at five-year follow-up (overall VE 80%; RR 0.20, 95% CI 0.15 to 0.26; 1 trial, 54,519 participants; high-certainty evidence). abstract, MAIN RESULTS Interval on the RR scale (RR 0.36, 95% CI 0.16 to 0.81). Certainty is moderate here, lower than at one and five years.
Cases of cholera at five-year follow-up severity: any case definition: Cholera cases as defined in the included randomised trial	children and adults aged 1 year and older country: India setting: urban slum, endemic (Kolkata) period: 2006-2011 n: 54,519 participants 1-4y5-11y12-17y18-49y50-64y65+	bivalent whole-cell vaccine (BivWC, Shanchol) platform: killed whole-cell doses: 2 time since vaccination: 5 years vs placebo, another vaccine, or no vaccine	80 (0.15–0.26 RR CI) VE (%)	systematic review GRADE: high 1 trial	Saif-Ur-Rahman et al. 2024 Cochrane Database Syst Rev quote Two doses of Shanchol reduces cases of cholera at one-year follow-up (overall VE 37%; RR 0.63, 95% CI 0.47 to 0.85; 2 trials, 241,631 participants; high-certainty evidence), at two-year follow-up (overall VE 64%; RR 0.36, 95% CI 0.16 to 0.81; 2 trials, 168,540 participants; moderate-certainty evidence), and at five-year follow-up (overall VE 80%; RR 0.20, 95% CI 0.15 to 0.26; 1 trial, 54,519 participants; high-certainty evidence). abstract, MAIN RESULTS Interval on the RR scale (RR 0.20, 95% CI 0.15 to 0.26). This rests on the single Kolkata trial, and Cochrane's figure is higher than the trial authors' own cumulative estimate because of a different analysis population; a reader should see both numbers rather than either alone.
Cases of cholera at six-month follow-up after a single dose severity: any case definition: Cholera cases as defined in the included randomised trial	children and adults aged 1 year and older country: Bangladesh setting: urban, highly endemic (Dhaka) period: 2014 n: 204,700 participants 1-4y5-11y12-17y18-49y50-64y65+	bivalent whole-cell vaccine (BivWC, Shanchol) platform: killed whole-cell doses: 1 time since vaccination: 6 months vs placebo, another vaccine, or no vaccine	40 (0.47–0.77 RR CI) VE (%)	systematic review GRADE: high 1 trial	Saif-Ur-Rahman et al. 2024 Cochrane Database Syst Rev quote A single dose of Shanchol reduces cases of cholera at six-month follow-up (overall VE 40%; RR 0.60, 95% CI 0.47 to 0.77; 1 trial, 204,700 participants; high-certainty evidence), and at two-year follow-up (overall VE 39%; RR 0.61, 95% CI 0.53 to 0.70; 1 trial, 204,700 participants; high-certainty evidence). abstract, MAIN RESULTS Interval on the RR scale (RR 0.60, 95% CI 0.47 to 0.77). Cochrane's single-dose estimates all come from one trial, the Dhaka trial, so they inherit its age pattern including no protection in under-5s.
Cases of cholera at two-year follow-up after a single dose severity: any case definition: Cholera cases as defined in the included randomised trial	children and adults aged 1 year and older country: Bangladesh setting: urban, highly endemic (Dhaka) period: 2014-2016 n: 204,700 participants 1-4y5-11y12-17y18-49y50-64y65+	bivalent whole-cell vaccine (BivWC, Shanchol) platform: killed whole-cell doses: 1 time since vaccination: 2 years vs placebo, another vaccine, or no vaccine	39 (0.53–0.70 RR CI) VE (%)	systematic review GRADE: high 1 trial	Saif-Ur-Rahman et al. 2024 Cochrane Database Syst Rev quote A single dose of Shanchol reduces cases of cholera at six-month follow-up (overall VE 40%; RR 0.60, 95% CI 0.47 to 0.77; 1 trial, 204,700 participants; high-certainty evidence), and at two-year follow-up (overall VE 39%; RR 0.61, 95% CI 0.53 to 0.70; 1 trial, 204,700 participants; high-certainty evidence). abstract, MAIN RESULTS Interval on the RR scale (RR 0.61, 95% CI 0.53 to 0.70).
Severe dehydrating cholera at six-month follow-up after a single dose severity: severe dehydration case definition: Cases of severe dehydrating cholera in the included randomised trial	children and adults aged 1 year and older country: Bangladesh setting: urban, highly endemic (Dhaka) period: 2014 n: 204,700 participants 1-4y5-11y12-17y18-49y50-64y65+	bivalent whole-cell vaccine (BivWC, Shanchol) platform: killed whole-cell doses: 1 time since vaccination: 6 months vs placebo, another vaccine, or no vaccine	63 (0.28–0.50 RR CI) VE (%)	systematic review GRADE: high 1 trial	Saif-Ur-Rahman et al. 2024 Cochrane Database Syst Rev quote A single dose of Shanchol also reduces cases of severe dehydrating cholera at six-month follow-up (overall VE 63%; RR 0.37, 95% CI 0.28 to 0.50; 1 trial, 204,700 participants; high-certainty evidence), and at two-year follow-up (overall VE 50%; RR 0.50, 95% CI 0.42 to 0.60; 1 trial, 204,700 participants; high-certainty evidence). abstract, MAIN RESULTS Interval on the RR scale (RR 0.37, 95% CI 0.28 to 0.50). High-certainty evidence that one dose halves or better the risk of the dehydrating disease that kills, within the first six months.
Severe dehydrating cholera at two-year follow-up after a single dose severity: severe dehydration case definition: Cases of severe dehydrating cholera in the included randomised trial	children and adults aged 1 year and older country: Bangladesh setting: urban, highly endemic (Dhaka) period: 2014-2016 n: 204,700 participants 1-4y5-11y12-17y18-49y50-64y65+	bivalent whole-cell vaccine (BivWC, Shanchol) platform: killed whole-cell doses: 1 time since vaccination: 2 years vs placebo, another vaccine, or no vaccine	50 (0.42–0.60 RR CI) VE (%)	systematic review GRADE: high 1 trial	Saif-Ur-Rahman et al. 2024 Cochrane Database Syst Rev quote A single dose of Shanchol also reduces cases of severe dehydrating cholera at six-month follow-up (overall VE 63%; RR 0.37, 95% CI 0.28 to 0.50; 1 trial, 204,700 participants; high-certainty evidence), and at two-year follow-up (overall VE 50%; RR 0.50, 95% CI 0.42 to 0.60; 1 trial, 204,700 participants; high-certainty evidence). abstract, MAIN RESULTS Interval on the RR scale (RR 0.50, 95% CI 0.42 to 0.60). Cochrane found no trials of Euvichol or Euvichol-Plus and applies the Shanchol results to them on the basis of comparable vibriocidal responses, which is an assumption a reader should know about.
Medically attended confirmed cholera severity: medically attended case definition: Medically attended, confirmed cholera	all ages in the included trials country: multiple setting: endemic and outbreak period: trials up to July 2016 n: 695 patients with cholera in 7 trials All ages	killed whole-cell oral cholera vaccines (kOCV) platform: killed whole-cell doses: 2 vs placebo or no vaccine in the included trials	58 (42–69) VE (%)	meta-analysis 7 trials	Bi et al. 2017 Lancet Infect Dis quote FINDINGS: Seven trials (with 695 patients with cholera) and six observational studies (217 patients with cholera) met the inclusion criteria, with an average two-dose efficacy of 58% (95% CI 42-69, I2=58%) and effectiveness of 76% (62-85, I2=0). abstract, FINDINGS Random-effects pooled efficacy from randomised trials, with substantial heterogeneity (I2=58%). The observational effectiveness figure from the same review is higher and is a separate record.
Medically attended confirmed cholera severity: medically attended case definition: Medically attended, confirmed cholera	all ages in the included observational studies country: multiple setting: endemic and outbreak period: studies up to July 2016 n: 217 patients with cholera in 6 observational studies All ages	killed whole-cell oral cholera vaccines (kOCV) platform: killed whole-cell doses: 2 vs unvaccinated people in the included case-control and cohort studies	76 (62–85) direct effectiveness (%)	meta-analysis 6 observational studies	Bi et al. 2017 Lancet Infect Dis quote FINDINGS: Seven trials (with 695 patients with cholera) and six observational studies (217 patients with cholera) met the inclusion criteria, with an average two-dose efficacy of 58% (95% CI 42-69, I2=58%) and effectiveness of 76% (62-85, I2=0). abstract, FINDINGS Observational effectiveness exceeds trial efficacy. Self-reported vaccination and healthcare-seeking differences can inflate case-control estimates, so the trial figure is the more conservative one.
Medically attended confirmed cholera in children under 5 severity: medically attended case definition: Medically attended, confirmed cholera	children younger than 5 years country: multiple setting: endemic and outbreak period: trials up to July 2016 Infant <1y1-4y	killed whole-cell oral cholera vaccines (kOCV) platform: killed whole-cell doses: 2 vs placebo or no vaccine	30 (15–42) VE (%)	meta-analysis	Bi et al. 2017 Lancet Infect Dis quote Average two-dose efficacy in children younger than 5 years (30% [95% CI 15-42], I2=0%) was lower than in those 5 years or older (64% [58-70], I2=0%; p<0·0001). abstract, FINDINGS Half the figure for people aged five and over, with the review reporting a highly significant difference, with no heterogeneity between studies. The age gap is the single most important qualifier on these vaccines.
Medically attended confirmed cholera in people aged 5 years or older severity: medically attended case definition: Medically attended, confirmed cholera	people aged 5 years or older country: multiple setting: endemic and outbreak period: trials up to July 2016 5-11y12-17y18-49y50-64y65+	killed whole-cell oral cholera vaccines (kOCV) platform: killed whole-cell doses: 2 vs placebo or no vaccine	64 (58–70) VE (%)	meta-analysis	Bi et al. 2017 Lancet Infect Dis quote Average two-dose efficacy in children younger than 5 years (30% [95% CI 15-42], I2=0%) was lower than in those 5 years or older (64% [58-70], I2=0%; p<0·0001). abstract, FINDINGS The comparator age band for the under-five record.
Medically attended confirmed cholera in the first year after vaccination severity: medically attended case definition: Medically attended, confirmed cholera	all ages in the included trials country: multiple setting: endemic and outbreak period: first year after vaccination All ages	killed whole-cell oral cholera vaccines (kOCV) platform: killed whole-cell doses: 2 time since vaccination: 0-12 months vs placebo or no vaccine	56 (42–66) VE (%) follow-up: first year	meta-analysis	Bi et al. 2017 Lancet Infect Dis quote Two-dose efficacy estimates of kOCV were similar during the first 2 years after vaccination, with estimates of 56% (95% CI 42-66, I2=45%) in the first year and 59% (49-67, I2=0) in the second year. abstract, FINDINGS The same sentence gives 59% (49-67) in the second year, filed separately: there is no measurable waning over the first two years.
Medically attended confirmed cholera in the second year after vaccination severity: medically attended case definition: Medically attended, confirmed cholera	all ages in the included trials country: multiple setting: endemic and outbreak period: second year after vaccination All ages	killed whole-cell oral cholera vaccines (kOCV) platform: killed whole-cell doses: 2 time since vaccination: 12-24 months vs placebo or no vaccine	59 (49–67) VE (%) follow-up: second year	meta-analysis	Bi et al. 2017 Lancet Infect Dis quote Two-dose efficacy estimates of kOCV were similar during the first 2 years after vaccination, with estimates of 56% (95% CI 42-66, I2=45%) in the first year and 59% (49-67, I2=0) in the second year. abstract, FINDINGS Indistinguishable from the first year.
Medically attended confirmed cholera in the third year after vaccination severity: medically attended case definition: Medically attended, confirmed cholera	all ages in the included trials country: multiple setting: endemic and outbreak period: third year after vaccination All ages	killed whole-cell oral cholera vaccines (kOCV) platform: killed whole-cell doses: 2 time since vaccination: 24-36 months vs placebo or no vaccine	39 (13–57) VE (%) follow-up: third year	meta-analysis	Bi et al. 2017 Lancet Infect Dis quote The efficacy reduced to 39% (13 to 57, I2=48%) in the third year, and 26% (-46 to 63, I2=74%) in the fourth year. abstract, FINDINGS The first clear drop. The review concludes two doses protect for at least 3 years.
Medically attended confirmed cholera in the fourth year after vaccination severity: medically attended case definition: Medically attended, confirmed cholera	all ages in the included trials country: multiple setting: endemic and outbreak period: fourth year after vaccination All ages	killed whole-cell oral cholera vaccines (kOCV) platform: killed whole-cell doses: 2 time since vaccination: 36-48 months vs placebo or no vaccine	26 (-46–63) VE (%) follow-up: fourth year	meta-analysis	Bi et al. 2017 Lancet Infect Dis quote The efficacy reduced to 39% (13 to 57, I2=48%) in the third year, and 26% (-46 to 63, I2=74%) in the fourth year. abstract, FINDINGS The interval spans zero with high heterogeneity (I2=74%): by the fourth year this evidence could not establish protection. The later update, with more data, still finds protection at four years, which is the record to read beside this one.
Medically attended confirmed cholera 12 months after vaccination severity: medically attended case definition: Medically attended, confirmed cholera	all ages in the included trials country: multiple setting: endemic, outbreak and humanitarian emergency period: studies published up to March 8, 2024 n: 5 RCTs and 10 observational studies All ages	killed whole-cell oral cholera vaccines (kOCV) platform: killed whole-cell doses: 2 time since vaccination: 12 months vs placebo or no vaccine in the included trials	55 (46–62) VE (%) follow-up: 12 months after vaccination	meta-analysis	Xu et al. 2025 Lancet Glob Health quote Average two-dose efficacy 12 months after vaccination was 55% (95% CI 46-62), declining to 44% (25-59) 48 months after vaccination. abstract, FINDINGS Meta-regression of efficacy as a function of time since vaccination; this is the most current pooled estimate for two doses.
Medically attended confirmed cholera 48 months after vaccination severity: medically attended case definition: Medically attended, confirmed cholera	all ages in the included trials country: multiple setting: endemic, outbreak and humanitarian emergency period: studies published up to March 8, 2024 All ages	killed whole-cell oral cholera vaccines (kOCV) platform: killed whole-cell doses: 2 time since vaccination: 48 months vs placebo or no vaccine in the included trials	44 (25–59) VE (%) follow-up: 48 months after vaccination	meta-analysis	Xu et al. 2025 Lancet Glob Health quote Average two-dose efficacy 12 months after vaccination was 55% (95% CI 46-62), declining to 44% (25-59) 48 months after vaccination. abstract, FINDINGS Protection at four years is lower than at one year but the interval still excludes zero, which is the basis for the review's conclusion of protection for at least 4 years.
Medically attended confirmed cholera 12 months after vaccination (observational) severity: medically attended case definition: Medically attended, confirmed cholera	all ages in the included observational studies country: multiple setting: endemic, outbreak and humanitarian emergency period: studies published up to March 8, 2024 All ages	killed whole-cell oral cholera vaccines (kOCV) platform: killed whole-cell doses: 2 time since vaccination: 12 months vs unvaccinated people in the included observational studies	69 (58–78) direct effectiveness (%) follow-up: 12 months after vaccination	meta-analysis	Xu et al. 2025 Lancet Glob Health quote Average two-dose effectiveness was 69% (58-78) 12 months after vaccination, declining to 47% (9-70) 48 months after vaccination. abstract, FINDINGS Field effectiveness again exceeds trial efficacy at the same time point; the review reports them separately rather than pooling them, and so does this file.
Medically attended confirmed cholera 48 months after vaccination (observational) severity: medically attended case definition: Medically attended, confirmed cholera	all ages in the included observational studies country: multiple setting: endemic, outbreak and humanitarian emergency period: studies published up to March 8, 2024 All ages	killed whole-cell oral cholera vaccines (kOCV) platform: killed whole-cell doses: 2 time since vaccination: 48 months vs unvaccinated people in the included observational studies	47 (9–70) direct effectiveness (%) follow-up: 48 months after vaccination	meta-analysis	Xu et al. 2025 Lancet Glob Health quote Average two-dose effectiveness was 69% (58-78) 12 months after vaccination, declining to 47% (9-70) 48 months after vaccination. abstract, FINDINGS A wide interval whose lower bound is close to zero.
Medically attended confirmed cholera 24 months after a single dose, age 5 and older severity: medically attended case definition: Medically attended, confirmed cholera	people 5 years and older country: Bangladesh setting: urban endemic period: the single one-dose RCT in the review 5-11y12-17y18-49y50-64y65+	killed whole-cell oral cholera vaccine (kOCV) platform: killed whole-cell doses: 1 time since vaccination: 24 months vs placebo	57 (42–69) VE (%) follow-up: 24 months	meta-analysis	Xu et al. 2025 Lancet Glob Health quote Only one RCT assessed one-dose efficacy and found sustained protection for 24 months (57% [42-69]) among those 5 years and older with no significant protection in younger children. abstract, FINDINGS The same sentence states there was no significant protection in younger children, which is the reason this estimate is restricted to those aged 5 and over.
Medically attended confirmed cholera 12 months after a single dose (observational) severity: medically attended case definition: Medically attended, confirmed cholera	all ages in the included observational studies country: multiple setting: endemic and outbreak period: studies published up to March 8, 2024 All ages	killed whole-cell oral cholera vaccines (kOCV) platform: killed whole-cell doses: 1 time since vaccination: 12 months vs unvaccinated people in the included observational studies	60 (51–68) direct effectiveness (%) follow-up: 12 months	meta-analysis	Xu et al. 2025 Lancet Glob Health quote Average one-dose effectiveness 12 months after vaccination was 60% (51-68) and after 24 months was 47% (34-58). abstract, FINDINGS The same sentence gives 47% (34-58) at 24 months, filed separately: one dose wanes faster than two.
Medically attended confirmed cholera 24 months after a single dose (observational) severity: medically attended case definition: Medically attended, confirmed cholera	all ages in the included observational studies country: multiple setting: endemic and outbreak period: studies published up to March 8, 2024 All ages	killed whole-cell oral cholera vaccines (kOCV) platform: killed whole-cell doses: 1 time since vaccination: 24 months vs unvaccinated people in the included observational studies	47 (34–58) direct effectiveness (%) follow-up: 24 months	meta-analysis	Xu et al. 2025 Lancet Glob Health quote Average one-dose effectiveness 12 months after vaccination was 60% (51-68) and after 24 months was 47% (34-58). abstract, FINDINGS The review's conclusion is that one dose protects for at least 2 years but wanes faster than two doses, and that under-5s are less protected regardless of dose number.
Cholera episodes in the first year after vaccination severity: any case definition: Cholera episodes as defined in the included large-scale efficacy trials	healthy adults and children in the included trials country: multiple setting: endemic period: trials up to October 2010 n: 249935 participants in 4 trials 1-4y5-11y12-17y18-49y50-64y65+	killed whole-cell oral cholera vaccines, five formulations platform: killed whole-cell doses: 2 or 3 as in the included trials vs placebo	52 (35–65) VE (%) follow-up: first year	systematic review	Sinclair et al. 2011 Cochrane Database Syst Rev quote The overall vaccine efficacy during the first year was 52% (95% CI 35% to 65%), and during the second year was 62% (95% CI 51% to 62%). abstract, MAIN RESULTS The superseded earlier Cochrane review, kept here for its age split and because it shows what the evidence base looked like before the Kolkata 5-year and Dhaka single-dose trials. The same sentence reports the second year as 62% with a 95% CI of 51% to 62%, an interval whose upper bound equals the point estimate; that is flagged in this file.
Cholera episodes in children under 5 severity: any case definition: Cholera episodes as defined in the included trials	children aged less than 5 years country: multiple setting: endemic period: trials up to October 2010 Infant <1y1-4y	killed whole-cell oral cholera vaccines platform: killed whole-cell doses: 2 or 3 as in the included trials vs placebo	38 (20–53) VE (%)	systematic review	Sinclair et al. 2011 Cochrane Database Syst Rev quote Protective efficacy was lower in children aged less than 5 years; 38% (95% CI 20% to 53%) compared to older children and adults; 66% (95% CI 57% to 73%).One trial of a killed whole cell vaccine amongst military recruits demonstrated 86% protective efficacy (95% CI 37% to 97%) in a small epidemic occurring within 4 weeks of the 2-dose schedule (one trial, 1426 participants). abstract, MAIN RESULTS The same sentence gives 66% (57% to 73%) in older children and adults. The under-5 deficit has been reproduced by every later review.
Cholera episodes in older children and adults severity: any case definition: Cholera episodes as defined in the included trials	older children and adults country: multiple setting: endemic period: trials up to October 2010 5-11y12-17y18-49y50-64y65+	killed whole-cell oral cholera vaccines platform: killed whole-cell doses: 2 or 3 as in the included trials vs placebo	66 (57–73) VE (%)	systematic review	Sinclair et al. 2011 Cochrane Database Syst Rev quote Protective efficacy was lower in children aged less than 5 years; 38% (95% CI 20% to 53%) compared to older children and adults; 66% (95% CI 57% to 73%).One trial of a killed whole cell vaccine amongst military recruits demonstrated 86% protective efficacy (95% CI 37% to 97%) in a small epidemic occurring within 4 weeks of the 2-dose schedule (one trial, 1426 participants). abstract, MAIN RESULTS The comparator band for the under-five record.
Cholera in a small epidemic among military recruits severity: any case definition: Cholera episodes during an epidemic within 4 weeks of the second dose	adult military recruits sex: predominantly male risk group: military recruits country: Peru setting: military, epidemic period: early 1990s n: 1426 participants 18-49y	killed whole-cell oral cholera vaccine platform: killed whole-cell doses: 2 time since vaccination: within 4 weeks vs placebo	86 (37–97) VE (%) follow-up: epidemic within 4 weeks of the 2-dose schedule	systematic review	Sinclair et al. 2011 Cochrane Database Syst Rev quote Protective efficacy was lower in children aged less than 5 years; 38% (95% CI 20% to 53%) compared to older children and adults; 66% (95% CI 57% to 73%).One trial of a killed whole cell vaccine amongst military recruits demonstrated 86% protective efficacy (95% CI 37% to 97%) in a small epidemic occurring within 4 weeks of the 2-dose schedule (one trial, 1426 participants). abstract, MAIN RESULTS Very short-term protection in healthy adults during an epidemic, from a single small trial; this is the Peruvian recruit trial, which is also recorded directly from its own publication.
Culture-confirmed Vibrio cholerae O1 diarrhoea severity: medically attended case definition: Culture-confirmed V. cholerae O1 diarrhoea severe enough to seek treatment in a health-care facility	non-pregnant individuals older than 1 year country: India setting: urban slum, endemic (Kolkata) period: 2006-2011 n: 66,900 fully dosed participants 1-4y5-11y12-17y18-49y50-64y65+	bivalent killed whole-cell oral cholera vaccine (Shanchol, Shantha Biotechnics) platform: killed whole-cell doses: 2 schedule: two doses 14 days apart time since vaccination: up to 5 years vs heat-killed Escherichia coli K12 placebo	65 (52–74) VE (%) follow-up: 14 to 1825 days after the second dose	RCT	Bhattacharya et al. 2013 Lancet Infect Dis quote Cumulative protective efficacy of the vaccine at 5 years was 65% (95% CI 52-74; p<0·0001), and point estimates by year of follow-up suggested no evidence of decline in protective efficacy. abstract, FINDINGS The strongest single piece of evidence for duration: the authors report point estimates by year of follow-up suggesting no decline over 5 years, which is longer sustained protection than any earlier oral cholera vaccine trial showed.
Culture-confirmed Vibrio cholerae O1 diarrhoea severity: medically attended case definition: Culture-confirmed V. cholerae O1 diarrhoea severe enough to seek treatment in a health-care facility	residents aged 1 year or older country: India setting: urban slum, endemic (Kolkata) period: 2006-2008 n: 66,900 fully dosed participants 1-4y5-11y12-17y18-49y50-64y65+	modified killed whole-cell bivalent oral cholera vaccine (Shanchol) platform: killed whole-cell doses: 2 vs heat-killed Escherichia coli K12 placebo	67 VE (%) follow-up: 14 to 730 days after the second dose	RCT	Sur et al. 2009 Lancet quote There were 20 episodes of cholera in the vaccine group and 68 episodes in the placebo group (protective efficacy 67%; one-tailed 99% CI, lower bound 35%, p<0.0001). abstract, FINDINGS The interim 2-year analysis. The source reports a one-tailed 99% confidence interval with a lower bound of 35%, which is not a two-sided interval, so no bounds are recorded here. The same abstract reports protection in the youngest age group with no significant difference between age groups, unlike the later Dhaka single-dose trial.
Culture-proven Vibrio cholerae O1 diarrhoea severity: medically attended case definition: Culture-proven V. cholerae O1 diarrhoea episodes severe enough to require treatment in a health care facility	residents 1 year of age and older country: India setting: urban slum, endemic (Kolkata) period: 2006-2009 n: 66,900 fully dosed individuals 1-4y5-11y12-17y18-49y50-64y65+	bivalent killed whole-cell oral cholera vaccine (Shanchol) platform: killed whole-cell doses: 2 vs heat-killed Escherichia coli K12 placebo	66 VE (%) follow-up: 3 years	RCT	Sur et al. 2011 PLoS Negl Trop Dis quote Of the 66,900 fully dosed individuals (31,932 vaccinees and 34,968 placebo recipients), 38 vaccinees and 128 placebo-recipients developed cholera during three years of follow-up (protective efficacy 66%; one-sided 95%CI lower bound = 53%, p<0.001). abstract, METHODS/PRINCIPAL FINDINGS The source reports a one-sided 95% confidence lower bound of 53%, not a two-sided interval, so no bounds are recorded.
Culture-proven Vibrio cholerae O1 diarrhoea in the third year after vaccination severity: medically attended case definition: Culture-proven V. cholerae O1 diarrhoea requiring health facility treatment	residents 1 year of age and older country: India setting: urban slum, endemic (Kolkata) period: third year of follow-up n: 66,900 fully dosed individuals 1-4y5-11y12-17y18-49y50-64y65+	bivalent killed whole-cell oral cholera vaccine (Shanchol) platform: killed whole-cell doses: 2 time since vaccination: 2-3 years vs heat-killed Escherichia coli K12 placebo	65 VE (%) follow-up: third year after the second dose	RCT	Sur et al. 2011 PLoS Negl Trop Dis quote Vaccine protection during the third year of follow-up was 65% (one-sided 95%CI lower bound = 44%, p<0.001). abstract, METHODS/PRINCIPAL FINDINGS A one-sided 95% lower bound of 44% is reported rather than a two-sided interval. The same abstract notes protection was evident in the second year in children vaccinated at 1-4 years and in the third year in older age groups.
Culture-confirmed cholera severity: any confirmed cholera case definition: Culture-confirmed cholera occurring 7 to 180 days after dosing	residents 1 year of age or older country: Bangladesh setting: urban, highly endemic (Dhaka) period: 2014 n: 204,700 recipients of one dose of vaccine or placebo 1-4y5-11y12-17y18-49y50-64y65+	killed bivalent whole-cell oral cholera vaccine (Shanchol) platform: killed whole-cell doses: 1 vs oral placebo	40 (11–60) VE (%) follow-up: 7 to 180 days after dosing	RCT	Qadri et al. 2016 N Engl J Med quote The vaccine protective efficacy was 40% (95% confidence interval [CI], 11 to 60%; 0.37 cases per 1000 vaccine recipients vs. abstract, RESULTS A single dose of a vaccine licensed as a two-dose course. Protection against all cholera is modest; the severe-dehydration estimate from the same trial is substantially higher and is the more decision-relevant number.
Severely dehydrating culture-confirmed cholera severity: severe dehydration case definition: Severely dehydrating culture-confirmed cholera 7 to 180 days after dosing	residents 1 year of age or older country: Bangladesh setting: urban, highly endemic (Dhaka) period: 2014 n: 204,700 recipients; 37 severely dehydrating episodes 1-4y5-11y12-17y18-49y50-64y65+	killed bivalent whole-cell oral cholera vaccine (Shanchol) platform: killed whole-cell doses: 1 vs oral placebo	63 (24–82) VE (%) follow-up: 7 to 180 days after dosing	RCT	Qadri et al. 2016 N Engl J Med quote 0.62 cases per 1000 placebo recipients) against all cholera episodes, 63% (95% CI, 24 to 82%; 0.10 vs. abstract, RESULTS Protection against the outcome that kills is higher than against all cholera episodes, a pattern repeated in the 2-year follow-up.
Culture-confirmed cholera in children vaccinated at 5 to 14 years severity: any confirmed cholera case definition: Culture-confirmed cholera 7 to 180 days after dosing	persons vaccinated at the age of 5 to 14 years country: Bangladesh setting: urban, highly endemic (Dhaka) period: 2014 5-11y12-17y	killed bivalent whole-cell oral cholera vaccine (Shanchol) platform: killed whole-cell doses: 1 vs oral placebo	63 (-39–90) VE (%) follow-up: 7 to 180 days after dosing	RCT	Qadri et al. 2016 N Engl J Med quote 0.26 cases per 1000 recipients) against severely dehydrating cholera episodes, and 63% (95% CI, -39 to 90%), 56% (95% CI, 16 to 77%), and 16% (95% CI, -49% to 53%) against all cholera episodes among persons vaccinated at the age of 5 to 14 years, 15 or more years, and 1 to 4 years, respectively, although the differences according to age were not significant (P=0.25). abstract, RESULTS The interval crosses zero: with few cases in this age band the trial could not establish protection, even though the point estimate is high. The abstract states the differences by age were not significant (P=0.25).
Culture-confirmed cholera in people vaccinated at 15 years or older severity: any confirmed cholera case definition: Culture-confirmed cholera 7 to 180 days after dosing	persons vaccinated at 15 or more years country: Bangladesh setting: urban, highly endemic (Dhaka) period: 2014 12-17y18-49y50-64y65+	killed bivalent whole-cell oral cholera vaccine (Shanchol) platform: killed whole-cell doses: 1 vs oral placebo	56 (16–77) VE (%) follow-up: 7 to 180 days after dosing	RCT	Qadri et al. 2016 N Engl J Med quote 0.26 cases per 1000 recipients) against severely dehydrating cholera episodes, and 63% (95% CI, -39 to 90%), 56% (95% CI, 16 to 77%), and 16% (95% CI, -49% to 53%) against all cholera episodes among persons vaccinated at the age of 5 to 14 years, 15 or more years, and 1 to 4 years, respectively, although the differences according to age were not significant (P=0.25). abstract, RESULTS The age band where single-dose protection is clearest.
Culture-confirmed cholera in children vaccinated at 1 to 4 years severity: any confirmed cholera case definition: Culture-confirmed cholera 7 to 180 days after dosing	persons vaccinated at the age of 1 to 4 years country: Bangladesh setting: urban, highly endemic (Dhaka) period: 2014 1-4y	killed bivalent whole-cell oral cholera vaccine (Shanchol) platform: killed whole-cell doses: 1 vs oral placebo	16 (-49–53) VE (%) follow-up: 7 to 180 days after dosing	RCT	Qadri et al. 2016 N Engl J Med quote 0.26 cases per 1000 recipients) against severely dehydrating cholera episodes, and 63% (95% CI, -39 to 90%), 56% (95% CI, 16 to 77%), and 16% (95% CI, -49% to 53%) against all cholera episodes among persons vaccinated at the age of 5 to 14 years, 15 or more years, and 1 to 4 years, respectively, although the differences according to age were not significant (P=0.25). abstract, RESULTS No demonstrated protection in the youngest children from a single dose. This is the central limitation of single-dose strategies, since young children carry much of the burden in endemic settings.
Culture-confirmed cholera over 2 years severity: any confirmed cholera case definition: Non-bloody diarrhoea with faecal culture positive for V. cholerae O1 or O139, onset at least 7 days after dosing	individuals aged 1 year or older country: Bangladesh setting: urban, highly endemic (Dhaka) period: 2014-2016 n: 204,700 in the per-protocol analysis 1-4y5-11y12-17y18-49y50-64y65+	killed bivalent whole-cell oral cholera vaccine (Shanchol) platform: killed whole-cell doses: 1 time since vaccination: up to 2 years vs oral placebo	39 (23–52) VE (%) follow-up: 7 to 730 days after dosing	RCT	Qadri et al. 2018 Lancet Infect Dis quote The overall incidence rates of initial cholera episodes were 0·22 (95% CI 0·18 to 0·27) per 100 000 person-days in vaccine recipients versus 0·36 (0·31 to 0·42) per 100 000 person-days in placebo recipients (adjusted protective efficacy 39%, 95% CI 23 to 52). abstract, FINDINGS Adjusted per-protocol estimate over the full 2 years. The sentence also carries incidence rates per person-day in each arm.
Severe cholera over 2 years severity: severe dehydration case definition: Culture-confirmed cholera episodes associated with severe dehydration	individuals aged 1 year or older country: Bangladesh setting: urban, highly endemic (Dhaka) period: 2014-2016 n: 138 severe episodes among 204,700 participants 1-4y5-11y12-17y18-49y50-64y65+	killed bivalent whole-cell oral cholera vaccine (Shanchol) platform: killed whole-cell doses: 1 time since vaccination: up to 2 years vs oral placebo	50 (29–65) VE (%) follow-up: 7 to 730 days after dosing	RCT	Qadri et al. 2018 Lancet Infect Dis quote The overall incidence of severe cholera was 0·09 (0·07 to 0·12) per 100 000 person-days versus 0·19 (0·15 to 0·23; adjusted protective efficacy 50%, 29 to 65). abstract, FINDINGS Protection against severe cholera stays higher than against all cholera at 2 years, as at 6 months.
Culture-confirmed cholera in children aged 5 to under 15 years severity: any confirmed cholera case definition: Culture-confirmed cholera over 2 years	participants aged 5 years to younger than 15 years country: Bangladesh setting: urban, highly endemic (Dhaka) period: 2014-2016 5-11y12-17y	killed bivalent whole-cell oral cholera vaccine (Shanchol) platform: killed whole-cell doses: 1 time since vaccination: up to 2 years vs oral placebo	52 (8–75) VE (%) follow-up: 2 years	RCT	Qadri et al. 2018 Lancet Infect Dis quote Vaccine protective efficacy was 52% (8 to 75) against all cholera episodes and 71% (27 to 88) against severe cholera episodes in participants aged 5 years to younger than 15 years. abstract, FINDINGS The same sentence gives 71% against severe cholera in this age band, filed separately.
Severe cholera in children aged 5 to under 15 years severity: severe dehydration case definition: Culture-confirmed cholera with severe dehydration over 2 years	participants aged 5 years to younger than 15 years country: Bangladesh setting: urban, highly endemic (Dhaka) period: 2014-2016 5-11y12-17y	killed bivalent whole-cell oral cholera vaccine (Shanchol) platform: killed whole-cell doses: 1 time since vaccination: up to 2 years vs oral placebo	71 (27–88) VE (%) follow-up: 2 years	RCT	Qadri et al. 2018 Lancet Infect Dis quote Vaccine protective efficacy was 52% (8 to 75) against all cholera episodes and 71% (27 to 88) against severe cholera episodes in participants aged 5 years to younger than 15 years. abstract, FINDINGS The highest single-dose estimate in the trial, in school-age children against the severe outcome.
Culture-confirmed cholera in participants aged 15 years or older severity: any confirmed cholera case definition: Culture-confirmed cholera over 2 years	participants aged 15 years or older country: Bangladesh setting: urban, highly endemic (Dhaka) period: 2014-2016 12-17y18-49y50-64y65+	killed bivalent whole-cell oral cholera vaccine (Shanchol) platform: killed whole-cell doses: 1 time since vaccination: up to 2 years vs oral placebo	59 (42–71) VE (%) follow-up: 2 years	RCT	Qadri et al. 2018 Lancet Infect Dis quote For participants aged 15 years or older, vaccine protective efficacy was 59% (42 to 71) against all cholera episodes and 59% (35 to 74) against severe cholera. abstract, FINDINGS The abstract states protection in the older age groups was sustained throughout the 2-year follow-up.
Severe cholera in participants aged 15 years or older severity: severe dehydration case definition: Culture-confirmed cholera with severe dehydration over 2 years	participants aged 15 years or older country: Bangladesh setting: urban, highly endemic (Dhaka) period: 2014-2016 12-17y18-49y50-64y65+	killed bivalent whole-cell oral cholera vaccine (Shanchol) platform: killed whole-cell doses: 1 time since vaccination: up to 2 years vs oral placebo	59 (35–74) VE (%) follow-up: 2 years	RCT	Qadri et al. 2018 Lancet Infect Dis quote For participants aged 15 years or older, vaccine protective efficacy was 59% (42 to 71) against all cholera episodes and 59% (35 to 74) against severe cholera. abstract, FINDINGS Unlike the younger age bands, adults show the same protection against all and severe cholera.
Culture-confirmed cholera in children younger than 5 years severity: any confirmed cholera case definition: Culture-confirmed cholera over 2 years	participants younger than 5 years country: Bangladesh setting: urban, highly endemic (Dhaka) period: 2014-2016 1-4y	killed bivalent whole-cell oral cholera vaccine (Shanchol) platform: killed whole-cell doses: 1 time since vaccination: up to 2 years vs oral placebo	-13 (-68–25) VE (%) follow-up: 2 years	RCT	Qadri et al. 2018 Lancet Infect Dis quote In participants younger than 5 years, the vaccine did not show protection against either all cholera episodes (protective efficacy -13%, -68 to 25) or severe cholera episodes (-44%, -220 to 35). abstract, FINDINGS A negative point estimate with an interval spanning zero, i.e. no protection demonstrated in under-5s from one dose. The authors suggest this reflects less pre-existing natural immunity in this age group. This record is why single-dose campaigns are not a substitute for two doses where young children are the target.
Severe cholera in children younger than 5 years severity: severe dehydration case definition: Culture-confirmed cholera with severe dehydration over 2 years	participants younger than 5 years country: Bangladesh setting: urban, highly endemic (Dhaka) period: 2014-2016 1-4y	killed bivalent whole-cell oral cholera vaccine (Shanchol) platform: killed whole-cell doses: 1 time since vaccination: up to 2 years vs oral placebo	-44 (-220–35) VE (%) follow-up: 2 years	RCT	Qadri et al. 2018 Lancet Infect Dis quote In participants younger than 5 years, the vaccine did not show protection against either all cholera episodes (protective efficacy -13%, -68 to 25) or severe cholera episodes (-44%, -220 to 35). abstract, FINDINGS A very wide interval around a negative point estimate: uninformative rather than evidence of harm, but it records that the trial found no severe-disease benefit of one dose in under-5s.
Severely dehydrating cholera in a vaccinated cluster severity: severe dehydration case definition: Risk of severely dehydrating cholera during 2 years after vaccination among all individuals present at the time of the second dose	urban residents of all ages present at the second dose country: Bangladesh setting: urban endemic, routine government delivery (Dhaka) period: 2011-2013 n: 94,675 in the vaccination-only group All ages	killed whole-cell oral cholera vaccine delivered through routine government services platform: killed whole-cell doses: 2 vs non-intervention clusters	37 overall protective effectiveness (%) follow-up: 2 years	cluster RCT	Qadri et al. 2015 Lancet quote Overall protective effectiveness was 37% (95% CI lower bound 18%; p=0·002) in the vaccination group and 45% (95% CI lower bound 24%; p=0·001) in the vaccination and behavioural change group. abstract, FINDINGS Overall (total) effectiveness at the coverage actually achieved, not per-protocol efficacy: it includes the unvaccinated residents of vaccinated clusters, so it is the figure a programme manager plans with. The source reports a one-sided 95% lower bound of 18%, not a two-sided interval. The same trial's vaccination-plus-behaviour-change arm is a separate record.
Severely dehydrating cholera in clusters given vaccine plus behaviour change severity: severe dehydration case definition: Risk of severely dehydrating cholera during 2 years after vaccination	urban residents of all ages present at the second dose country: Bangladesh setting: urban endemic, routine government delivery (Dhaka) period: 2011-2013 n: 92,539 in the vaccination and behavioural change group All ages	killed whole-cell oral cholera vaccine plus handwashing and safe drinking water promotion platform: killed whole-cell doses: 2 vs non-intervention clusters	45 overall protective effectiveness (%) follow-up: 2 years	cluster RCT	Qadri et al. 2015 Lancet quote Overall protective effectiveness was 37% (95% CI lower bound 18%; p=0·002) in the vaccination group and 45% (95% CI lower bound 24%; p=0·001) in the vaccination and behavioural change group. abstract, FINDINGS Adding water and hygiene promotion to vaccination gave a higher point estimate than vaccination alone (37%), but the trial was not powered to establish that the difference is real. One-sided lower bound only.
Confirmed cholera within 6 months of the third dose severity: medically attended case definition: Cases of confirmed cholera seeking medical care up to six months after the third dose	children aged 2-15 years and women aged over 15 years sex: children of both sexes and adult women only country: Bangladesh setting: rural endemic (Matlab) period: 1985 n: 63 498 participants 1-4y5-11y12-17y18-49y50-64y65+	B subunit killed whole-cell oral cholera vaccine (BS-WC, the formulation marketed as Dukoral) platform: killed whole-cell with recombinant B subunit doses: 3 vs placebo	85 VE (%) follow-up: up to 6 months after the third dose	RCT	Clemens et al. 1986 Lancet quote Surveillance for cases seeking medical care up to six months after the third dose revealed 26 cases of confirmed cholera in the placebo group, 4 cases in the BS-WC group (protective efficacy 85%; p less than 0.0001), and 11 cases in the WC group (protective efficacy 58%; p less than 0.01). abstract The first six months only; the same trial's later reports show this high early figure falling steeply. The abstract gives a p value, not a confidence interval.
Confirmed cholera within 6 months of the third dose severity: medically attended case definition: Cases of confirmed cholera seeking medical care up to six months after the third dose	children aged 2-15 years and women aged over 15 years sex: children of both sexes and adult women only country: Bangladesh setting: rural endemic (Matlab) period: 1985 n: 63 498 participants 1-4y5-11y12-17y18-49y50-64y65+	killed whole-cell-only oral cholera vaccine (WC, no B subunit) platform: killed whole-cell doses: 3 vs placebo	58 VE (%) follow-up: up to 6 months after the third dose	RCT	Clemens et al. 1986 Lancet quote Surveillance for cases seeking medical care up to six months after the third dose revealed 26 cases of confirmed cholera in the placebo group, 4 cases in the BS-WC group (protective efficacy 85%; p less than 0.0001), and 11 cases in the WC group (protective efficacy 58%; p less than 0.01). abstract The whole-cell-only arm, without the B subunit, in the same trial and period as the B subunit record above. The B subunit advantage seen here disappears by one year.
Cholera within one year of vaccination severity: medically attended case definition: Cases of cholera detected in surveillance over one complete year	children and women residing in rural Bangladesh sex: children of both sexes and adult women only country: Bangladesh setting: rural endemic (Matlab) period: 1985-1986 n: 62,285 participants 1-4y5-11y12-17y18-49y50-64y65+	B subunit killed whole-cell oral cholera vaccine (BS-WC) platform: killed whole-cell with B subunit doses: 3 vs placebo	62 VE (%) follow-up: 1 year	RCT	Clemens et al. 1988 J Infect Dis quote After one complete year of surveillance, 110 cases of cholera were detected in the placebo group, 52 in the WC group (PE, 53%; P less than .0001), and 41 in the BS-WC group (PE, 62%; P less than .0001). abstract The abstract states the B subunit advantage over whole-cell-only held only during the first eight months, and that protection was high and sustained in those vaccinated over five years of age but transient in younger children.
Cholera within one year of vaccination severity: medically attended case definition: Cases of cholera detected in surveillance over one complete year	children and women residing in rural Bangladesh sex: children of both sexes and adult women only country: Bangladesh setting: rural endemic (Matlab) period: 1985-1986 n: 62,285 participants 1-4y5-11y12-17y18-49y50-64y65+	killed whole-cell-only oral cholera vaccine (WC) platform: killed whole-cell doses: 3 vs placebo	53 VE (%) follow-up: 1 year	RCT	Clemens et al. 1988 J Infect Dis quote After one complete year of surveillance, 110 cases of cholera were detected in the placebo group, 52 in the WC group (PE, 53%; P less than .0001), and 41 in the BS-WC group (PE, 62%; P less than .0001). abstract The same abstract reports that both vaccines protected equally against life-threatening dehydration and against less severe cholera.
Cholera over 3 years of follow-up severity: medically attended case definition: Cholera cases in trial surveillance	children aged 2-15 years and women over 15 years sex: children of both sexes and adult women only country: Bangladesh setting: rural endemic (Matlab) period: 1985-1988 n: 62 285 subjects who received three doses 1-4y5-11y12-17y18-49y50-64y65+	B subunit killed whole-cell oral cholera vaccine (BS-WC) platform: killed whole-cell with B subunit doses: 3 time since vaccination: up to 3 years vs Escherichia coli K12 strain placebo	50 VE (%) follow-up: 3 years	RCT	Clemens et al. 1990 Lancet quote Among the 62 285 subjects who received three doses of BS-WC, WC, or Escherichia coli K12 strain placebo, cumulative PE at 3 years of follow-up was 50% for BS-WC and 52% for WC. abstract Cumulative 3-year efficacy, about half the 6-month figure: this is the waning that the later two-dose Shanchol trials did not show over 5 years.
Cholera over 3 years of follow-up severity: medically attended case definition: Cholera cases in trial surveillance	children aged 2-15 years and women over 15 years sex: children of both sexes and adult women only country: Bangladesh setting: rural endemic (Matlab) period: 1985-1988 n: 62 285 subjects who received three doses 1-4y5-11y12-17y18-49y50-64y65+	killed whole-cell-only oral cholera vaccine (WC) platform: killed whole-cell doses: 3 time since vaccination: up to 3 years vs Escherichia coli K12 strain placebo	52 VE (%) follow-up: 3 years	RCT	Clemens et al. 1990 Lancet quote Among the 62 285 subjects who received three doses of BS-WC, WC, or Escherichia coli K12 strain placebo, cumulative PE at 3 years of follow-up was 50% for BS-WC and 52% for WC. abstract By 3 years the two formulations are indistinguishable, so the B subunit contributes early protection only.
Cholera over 3 years in children vaccinated at 2-5 years severity: medically attended case definition: Cholera cases in trial surveillance	children vaccinated at 2-5 years country: Bangladesh setting: rural endemic (Matlab) period: 1985-1988 1-4y5-11y	B subunit killed whole-cell oral cholera vaccine (BS-WC) platform: killed whole-cell with B subunit doses: 3 time since vaccination: up to 3 years vs Escherichia coli K12 strain placebo	26 VE (%) follow-up: 3 years	RCT	Clemens et al. 1990 Lancet quote PE was similar against severe and non-severe cholera, but was significantly lower in children who were vaccinated at 2-5 years (26% for BS-WC; 23% for WC) than in older persons (63% for BS-WC; 68% for WC). abstract Significantly lower than in older vaccinees. The same sentence gives 23% for the whole-cell-only vaccine in this age band.
Cholera over 3 years in people vaccinated above 5 years of age severity: medically attended case definition: Cholera cases in trial surveillance	persons vaccinated at older than 2-5 years, described as older persons country: Bangladesh setting: rural endemic (Matlab) period: 1985-1988 5-11y12-17y18-49y50-64y65+	B subunit killed whole-cell oral cholera vaccine (BS-WC) platform: killed whole-cell with B subunit doses: 3 time since vaccination: up to 3 years vs Escherichia coli K12 strain placebo	63 VE (%) follow-up: 3 years	RCT	Clemens et al. 1990 Lancet quote PE was similar against severe and non-severe cholera, but was significantly lower in children who were vaccinated at 2-5 years (26% for BS-WC; 23% for WC) than in older persons (63% for BS-WC; 68% for WC). abstract More than double the figure for 2-5 year olds. The age gap seen in this early report is the same gap the most recent meta-analysis still reports.
Cholera during the third year of follow-up in older vaccinees severity: medically attended case definition: Cholera cases in the third year of trial surveillance	persons vaccinated at older ages country: Bangladesh setting: rural endemic (Matlab) period: third year of follow-up, 1987-1988 5-11y12-17y18-49y50-64y65+	B subunit killed whole-cell oral cholera vaccine (BS-WC) platform: killed whole-cell with B subunit doses: 3 time since vaccination: 2-3 years vs Escherichia coli K12 strain placebo	40 VE (%) follow-up: third year after vaccination	RCT	Clemens et al. 1990 Lancet quote In contrast, persons vaccinated at older ages were protected even in the third year of follow-up (PE 40% for BS-WC; 62% for WC). abstract The same sentence gives 62% for the whole-cell-only vaccine in the third year. In children vaccinated at 2-5 years, protection had waned rapidly after 4-6 months and was not evident in the third year at all.
Cholera caused by the classical biotype severity: medically attended case definition: Cholera cases in trial surveillance, classical biotype	children aged 2-15 years and women over 15 years country: Bangladesh setting: rural endemic (Matlab) period: 1985-1988 1-4y5-11y12-17y18-49y50-64y65+	B subunit killed whole-cell oral cholera vaccine (BS-WC) platform: killed whole-cell with B subunit doses: 3 vs Escherichia coli K12 strain placebo	58 VE (%) follow-up: 3 years	RCT	Clemens et al. 1990 Lancet quote PE was substantially higher against classical cholera (58% for BS-WC; 60% for WC) than against El Tor cholera (39% and 40%). abstract Strain matters: protection against the classical biotype was substantially higher than against El Tor, which is the biotype responsible for the current pandemic.
Cholera caused by the El Tor biotype severity: medically attended case definition: Cholera cases in trial surveillance, El Tor biotype	children aged 2-15 years and women over 15 years country: Bangladesh setting: rural endemic (Matlab) period: 1985-1988 1-4y5-11y12-17y18-49y50-64y65+	B subunit killed whole-cell oral cholera vaccine (BS-WC) platform: killed whole-cell with B subunit doses: 3 vs Escherichia coli K12 strain placebo	39 VE (%) follow-up: 3 years	RCT	Clemens et al. 1990 Lancet quote PE was substantially higher against classical cholera (58% for BS-WC; 60% for WC) than against El Tor cholera (39% and 40%). abstract The figure for the biotype that actually circulates today; the sentence gives 40% for the whole-cell-only vaccine. The pooled three-year figure mixes both biotypes.
Cholera over 5 years of follow-up severity: medically attended case definition: Cases of cholera during 5 years of follow-up	children over 2 years and adult women sex: children of both sexes and adult women only country: Bangladesh setting: rural endemic (Matlab) period: 1985-1990 n: 62285 participants 1-4y5-11y12-17y18-49y50-64y65+	B subunit killed whole-cell oral cholera vaccine (BS-WC) platform: killed whole-cell with B subunit doses: 3 time since vaccination: up to 5 years vs Escherichia coli K12 placebo	49 VE (%) follow-up: 5 years	RCT	van et al. 1996 Vaccine quote During 5 years of follow-up, there were 144 cases of cholera in the BS-WC group (PE = 49%; P < 0.001), 150 in the WC group (PE = 47%; P < 0.001), and 283 in the K12 group. abstract The cumulative 5-year figure is almost unchanged from the 3-year figure because, as the abstract states, protection by each vaccine was evident only during the first three years; the later years add cases to both arms without adding protection.
Cholera over 5 years of follow-up severity: medically attended case definition: Cases of cholera during 5 years of follow-up	children over 2 years and adult women sex: children of both sexes and adult women only country: Bangladesh setting: rural endemic (Matlab) period: 1985-1990 n: 62285 participants 1-4y5-11y12-17y18-49y50-64y65+	killed whole-cell-only oral cholera vaccine (WC) platform: killed whole-cell doses: 3 time since vaccination: up to 5 years vs Escherichia coli K12 placebo	47 VE (%) follow-up: 5 years	RCT	van et al. 1996 Vaccine quote During 5 years of follow-up, there were 144 cases of cholera in the BS-WC group (PE = 49%; P < 0.001), 150 in the WC group (PE = 47%; P < 0.001), and 283 in the K12 group. abstract The abstract adds that long-term protection of young children was seen only against classical, not El Tor, cholera.
Moderate to severe diarrhoeal purge after experimental challenge severity: moderate to severe diarrhoea case definition: Moderate (at least 3.0 L) to severe (at least 5.0 L) diarrhoeal purge after ingesting wild-type V. cholerae O1 El Tor Inaba N16961	healthy adults 18-45 years old risk group: healthy volunteers, cholera-naive country: United States setting: inpatient research ward period: 2013-2015 n: 95 vaccinees and 102 placebo recipients 18-49y	PXVX0200 live attenuated CVD 103-HgR (Vaxchora) platform: live attenuated doses: 1 time since vaccination: 10 days vs placebo	90.3 VE (%) follow-up: challenge 10 days after vaccination	RCT	Chen et al. 2016 Clin Infect Dis quote The primary endpoint, moderate (≥3.0 L) to severe (≥5.0 L) diarrheal purge, occurred in 39 of 66 (59.1%) placebo controls but only 2 of 35 (5.7%) vaccinees at 10 days (vaccine efficacy, 90.3%; P < .0001) and 4 of 33 (12.1%) vaccinees at 3 months (vaccine efficacy, 79.5%; P < .0001). abstract, RESULTS An experimental challenge in cholera-naive US adults, not a field trial: the challenge dose and the absence of pre-existing immunity are both unlike endemic settings, and the endpoint is purge volume. The abstract gives a p value, not a confidence interval.
Moderate to severe diarrhoeal purge after experimental challenge at 3 months severity: moderate to severe diarrhoea case definition: Moderate to severe diarrhoeal purge after experimental V. cholerae O1 El Tor challenge	healthy adults 18-45 years old risk group: healthy volunteers, cholera-naive country: United States setting: inpatient research ward period: 2013-2015 n: 33 vaccinees challenged at 3 months 18-49y	PXVX0200 live attenuated CVD 103-HgR (Vaxchora) platform: live attenuated doses: 1 time since vaccination: 3 months vs placebo	79.5 VE (%) follow-up: challenge 3 months after vaccination	RCT	Chen et al. 2016 Clin Infect Dis quote The primary endpoint, moderate (≥3.0 L) to severe (≥5.0 L) diarrheal purge, occurred in 39 of 66 (59.1%) placebo controls but only 2 of 35 (5.7%) vaccinees at 10 days (vaccine efficacy, 90.3%; P < .0001) and 4 of 33 (12.1%) vaccinees at 3 months (vaccine efficacy, 79.5%; P < .0001). abstract, RESULTS This is the longest interval at which Vaxchora efficacy has been measured; CDC states duration of protection beyond three months is uncertain. These are the two numbers behind the travel-vaccine label.
Moderate or severe diarrhoea after experimental challenge severity: moderate to severe diarrhoea case definition: Moderate or severe diarrhoea, at least 3 litres of diarrhoeal stool, after challenge with V. cholerae O1 El Tor Inaba N16961	adult volunteers risk group: healthy volunteers country: United States setting: inpatient challenge study period: 1990s n: 28 vaccinees and 23 placebo recipients challenged 18-49y	CVD 103-HgR live attenuated oral cholera vaccine (earlier formulation) platform: live attenuated doses: 1 time since vaccination: about 3 months vs killed E. coli K-12 placebo	91 VE (%) follow-up: challenge about 3 months after immunisation	RCT	Tacket et al. 1999 Infect Immun quote After challenge, 9 (39%) of the 23 placebo recipients and 1 (4%) of the 28 vaccinees had moderate or severe diarrhea (>/=3-liter diarrheal stool) (P < 0.01; protective efficacy, 91%). abstract An earlier formulation of the same live vaccine strain, challenged at 3 months. Very small numbers (fewer than sixty volunteers challenged in total) and no confidence interval reported.
Any diarrhoea after experimental challenge severity: any diarrhoea case definition: Any diarrhoea after challenge with V. cholerae O1 El Tor Inaba N16961	adult volunteers risk group: healthy volunteers country: United States setting: inpatient challenge study period: 1990s n: 28 vaccinees and 23 placebo recipients challenged 18-49y	CVD 103-HgR live attenuated oral cholera vaccine (earlier formulation) platform: live attenuated doses: 1 time since vaccination: about 3 months vs killed E. coli K-12 placebo	80 VE (%) follow-up: challenge about 3 months after immunisation	RCT	Tacket et al. 1999 Infect Immun quote A total of 21 (91%) of 23 placebo recipients and 5 (18%) of 28 vaccinees had any diarrhea (P < 0.001; protective efficacy, 80%). abstract Against any diarrhoea rather than the severe endpoint, the figure is lower, as expected. Note that 91% of placebo recipients developed diarrhoea after challenge, an attack rate no field setting approaches.
Cholera requiring inpatient care severity: hospitalisation case definition: Cholera requiring inpatient care during an El Tor outbreak 8-10 months after vaccination	people at least 1 year old country: Viet Nam setting: urban field trial by household allocation (Hue) period: outbreak 8-10 months after vaccination n: 51,975 people who received the complete two-dose regimen 1-4y5-11y12-17y18-49y50-64y65+	killed whole-cell oral cholera vaccine produced in Viet Nam platform: killed whole-cell doses: 2 time since vaccination: 8-10 months vs the no-vaccine group (alternate households)	66 (46–79) VE (%) follow-up: 8-10 months	RCT	Trach et al. 1997 Lancet quote Among the 51,975 people who received the complete two-dose vaccine regimen, the protective efficacy was 66% (46-79): in this subset, the protective efficacy was similar for children aged 1-5 years (68%) and for older people (66%). abstract, FINDINGS An open, alternate-household allocation rather than a blinded randomisation. The abstract states protection was similar in children aged 1-5 years (68%) and older people (66%), which is the exception to the usual under-5 deficit and was the reason this vaccine was developed into Shanchol.
Cholera requiring inpatient care, intention-to-treat severity: hospitalisation case definition: Cholera requiring inpatient care among all age-eligible people allocated to vaccine	people at least 1 year old country: Viet Nam setting: urban field trial (Hue) period: outbreak 8-10 months after vaccination n: 67,395 allocated to vaccine and 67,058 to no vaccine 1-4y5-11y12-17y18-49y50-64y65+	killed whole-cell oral cholera vaccine produced in Viet Nam platform: killed whole-cell doses: 2 as allocated, including incomplete dosing vs the no-vaccine group	60 (40–73) protective impact (%) by intention to treat follow-up: 8-10 months	RCT	Trach et al. 1997 Lancet quote FINDINGS: During an outbreak of El Tor cholera 8-10 months after vaccination, 37 cases of cholera requiring inpatient care occurred among age-eligible people allocated to the vaccine group, and 92 cases among age-eligible people allocated to the no-vaccine group (protective impact 60% [95% CI 40-73]). abstract, FINDINGS Intention-to-treat, so it includes people allocated vaccine who did not complete both doses: lower than the per-protocol estimate and closer to what a programme achieves.
Symptomatic cholera in military recruits severity: symptomatic case definition: Vibrio cholerae O1 El Tor Ogawa isolated from subjects with diarrhoea, 2 weeks or longer after the second dose	adult military recruits sex: men risk group: military recruits, 76% blood group O country: Peru setting: military, epidemic period: early 1990s n: 1426 recruits who received two doses 18-49y	whole-cell/recombinant B subunit vaccine (WC/rBS, Dukoral) platform: killed whole-cell with recombinant B subunit doses: 2 doses 7-14 days apart time since vaccination: 2 weeks to about 5 months vs Escherichia coli K12 placebo	86 (37–97) VE (%) follow-up: mean 18 weeks	RCT	Sanchez et al. 1994 Lancet quote The vaccine had significant protective efficacy against cholera (86% [95% CI 37-97], p < 0.01) but not against symptomless infection (42% [-96 to 85]). abstract Short-term protection in healthy adults, with only seventeen cholera cases in total. All cases occurred in people of blood group O.
Symptomless Vibrio cholerae infection severity: asymptomatic infection case definition: Symptomless infection detected 2 weeks or longer after the second dose	adult military recruits sex: men risk group: military recruits country: Peru setting: military, epidemic period: early 1990s n: 14 symptomless infections detected 18-49y	whole-cell/recombinant B subunit vaccine (WC/rBS, Dukoral) platform: killed whole-cell with recombinant B subunit doses: 2 vs Escherichia coli K12 placebo	42 (-96–85) VE (%) follow-up: mean 18 weeks	RCT	Sanchez et al. 1994 Lancet quote The vaccine had significant protective efficacy against cholera (86% [95% CI 37-97], p < 0.01) but not against symptomless infection (42% [-96 to 85]). abstract No demonstrated effect on asymptomatic infection: these vaccines are measured against disease, not against carriage, so transmission blocking cannot be inferred from the disease estimates.
Cholera, direct protection after adjusting for neighbourhood vaccine coverage severity: medically attended case definition: Cholera in the first year of trial surveillance	children and adult women sex: children of both sexes and adult women country: Bangladesh setting: rural endemic (Matlab) period: first year of the 1985 trial 1-4y5-11y12-17y18-49y50-64y65+	B subunit killed whole-cell and killed whole-cell-only oral cholera vaccines platform: killed whole-cell doses: 3 vs placebo recipients, adjusted for the vaccine coverage of the residential cluster	55 (41–66) VE (%) adjusted for cluster coverage follow-up: first year	RCT	Ali et al. 2005 Lancet quote Moreover, after adjustment for the level of vaccine coverage of the cluster, vaccine protective efficacy remained significant (55% [95% CI 41-66], p<0.0001). abstract, FINDINGS The direct effect that survives after the herd effect is accounted for: being vaccinated and living among vaccinated neighbours protect independently.
Cholera in unvaccinated placebo recipients in highly vaccinated clusters (herd protection) severity: medically attended case definition: Cholera among placebo recipients by quintile of cluster vaccine coverage	children and adult women vaccination status: unvaccinated country: Bangladesh setting: rural endemic (Matlab) period: first year of the 1985 trial 1-4y5-11y12-17y18-49y50-64y65+	B subunit killed whole-cell and killed whole-cell-only oral cholera vaccines platform: killed whole-cell doses: 3 (received by neighbours, not by these individuals) vs placebo recipients in the lowest coverage quintile, 7.01 per 1000	1.47 cholera incidence per 1000 placebo recipients, highest coverage quintile follow-up: first year	RCT	Ali et al. 2005 Lancet quote Incidence rates of cholera among placebo recipients were inversely related to levels of vaccine coverage (7.01 cases per 1000 in the lowest quintile of coverage vs 1.47 cases per 1000 in the highest quintile; p<0.0001 for trend). abstract, FINDINGS Indirect protection: unvaccinated people in the most vaccinated neighbourhoods had roughly a fifth the cholera incidence of unvaccinated people in the least vaccinated ones, with cluster coverage ranging widely. Observational within a randomised trial, so neighbourhood confounding cannot be fully excluded, though the authors adjusted for measured confounders.
Cholera in the 8 to 28 days after exposure to a case, high versus low coverage rings severity: medically attended case definition: Cholera among people living within 25 m of a cholera case, 8-28 days after onset in the index case	ring residents of all ages country: India setting: urban slum, endemic (Kolkata) period: first 2 years after vaccination n: 144,106 individuals under surveillance All ages	bivalent killed whole-cell oral cholera vaccine (Shanchol) platform: killed whole-cell doses: 2 time since vaccination: up to 2 years vs residents of low vaccine-coverage rings, irrespective of individual vaccination status	91 (62–98) overall VE (%) in a high-coverage ring follow-up: 8-28 days after exposure, within the first 2 years	RCT	Ali et al. 2016 PLoS Med quote The overall and indirect VE measured between 8 and 28 d after exposure to a cholera index case during the first 2 y was 91% (95% CI 62%-98%) and 93% (95% CI 44%-99%), respectively. abstract, METHODS AND FINDINGS A reanalysis of the Kolkata trial, not a trial of ring vaccination: everyone here received two doses months earlier. It shows what protection looks like in the high-risk days after a neighbour falls ill, and the authors caution that a single dose given quickly may not reproduce it.
Cholera in unvaccinated members of high-coverage rings (indirect protection) severity: medically attended case definition: Cholera among unvaccinated people living within 25 m of a cholera case	ring residents of all ages vaccination status: unvaccinated country: India setting: urban slum, endemic (Kolkata) period: first 2 years after vaccination All ages	bivalent killed whole-cell oral cholera vaccine (Shanchol) platform: killed whole-cell doses: 2 (received by neighbours) time since vaccination: up to 2 years vs unvaccinated members of low-coverage rings	93 (44–99) indirect VE (%) for unvaccinated members of a high-coverage ring follow-up: 8-28 days after exposure, within the first 2 years	RCT	Ali et al. 2016 PLoS Med quote The overall and indirect VE measured between 8 and 28 d after exposure to a cholera index case during the first 2 y was 91% (95% CI 62%-98%) and 93% (95% CI 44%-99%), respectively. abstract, METHODS AND FINDINGS The indirect estimate is as high as the overall one, with a much wider interval. The same paper reports that protection persisted for 5 years and did not depend on whether the index case was a child under 5.
Rapid-test-confirmed cholera during an outbreak severity: medically attended case definition: Suspected cholera confirmed by rapid test	case patients and neighbourhood controls of the same age and sex country: Guinea setting: outbreak response, reactive campaign period: May to October 2012 n: 40 case patients and 160 controls All ages	bivalent killed whole-cell oral cholera vaccine (Shanchol) platform: killed whole-cell doses: 2 complete doses vs unvaccinated neighbourhood controls matched on age and sex	86.6 (56.7–95.8) VE (%) follow-up: first months after vaccination	case-control	Luquero et al. 2014 N Engl J Med quote After adjustment for potentially confounding variables, vaccination with two complete doses was associated with significant protection against cholera (effectiveness, 86.6%; 95% confidence interval, 56.7 to 95.8; P=0.001). abstract, RESULTS The first field effectiveness estimate for Shanchol used reactively in an African outbreak, and the short-term estimate the global stockpile was built on. Only forty cases, so the interval is wide, and vaccination status was partly self-reported.
Culture-confirmed cholera after a reactive campaign severity: medically attended case definition: Acute watery diarrhoea with a stool sample positive for cholera by culture, in people who sought treatment	people aged 12 months and older eligible for the campaign pregnancy: pregnant women were excluded from the campaign country: Haiti setting: rural, reactive campaign in a newly epidemic country period: October 2012 to March 2014 n: 47 cases and 188 matched controls 1-4y5-11y12-17y18-49y50-64y65+	oral inactivated bivalent whole-cell vaccine (Shanchol) platform: killed whole-cell doses: 2 time since vaccination: 4-24 months vs matched community controls who did not seek treatment for acute watery diarrhoea	63 (8–85) VE (%) follow-up: 4 to 24 months after vaccination	case-control	Ivers et al. 2015 Lancet Glob Health quote 33 (70%) of 47 cholera cases self-reported vaccination versus 167 (89%) of 188 controls (vaccine effectiveness 63%, 95% CI 8-85). abstract, FINDINGS Based on self-reported vaccination; the same study's estimate using certified vaccination cards is lower and is filed separately. The bias-indicator analysis found no association with non-cholera diarrhoea.
Culture-confirmed cholera, certified vaccination only severity: medically attended case definition: Culture-confirmed cholera in people with documented vaccination	people aged 12 months and older eligible for the campaign country: Haiti setting: rural, reactive campaign period: October 2012 to March 2014 n: 47 cases and 188 matched controls 1-4y5-11y12-17y18-49y50-64y65+	oral inactivated bivalent whole-cell vaccine (Shanchol) platform: killed whole-cell doses: 2 time since vaccination: 4-24 months vs matched community controls without acute watery diarrhoea	58 (13–80) VE (%) follow-up: 4 to 24 months after vaccination	case-control	Ivers et al. 2015 Lancet Glob Health quote 27 (57%) of 47 cases had certified vaccination versus 147 (78%) of 188 controls (vaccine effectiveness 58%, 13-80). abstract, FINDINGS Using verified cards rather than self-report moves the estimate down by 5 percentage points, which is the size of the recall-bias effect in this study.
Non-cholera diarrhoea (bias indicator, negative control outcome) severity: medically attended case definition: Acute watery diarrhoea with a stool sample negative for cholera	people aged 12 months and older eligible for the campaign country: Haiti setting: rural, reactive campaign period: October 2012 to March 2014 n: 42 bias-indicator cases 1-4y5-11y12-17y18-49y50-64y65+	oral inactivated bivalent whole-cell vaccine (Shanchol) platform: killed whole-cell doses: 2 vs matched community controls without acute watery diarrhoea	18 (-208–78) apparent VE (%) against non-cholera diarrhoea	case-control	Ivers et al. 2015 Lancet Glob Health quote Neither self-reported nor verified vaccination was significantly associated with non-cholera diarrhoea (vaccine effectiveness 18%, 95% CI -208 to 78 by self-report and -21%, -238 to 57 by verified vaccination). abstract, FINDINGS A negative-control outcome, not a benefit: a cholera vaccine should not prevent non-cholera diarrhoea, and this interval includes zero. It is the check that the cholera estimate is not simply healthier people getting vaccinated.
Culture-confirmed cholera up to 4 years after vaccination severity: medically attended case definition: Positive stool culture in patients recruited from cholera treatment centres	people aged 12 months and older eligible for the campaign country: Haiti setting: epidemic and newly endemic, Artibonite and Central Departments period: October 2012 to November 2016 n: 178 cases and 706 controls 1-4y5-11y12-17y18-49y50-64y65+	killed bivalent whole-cell oral cholera vaccine platform: killed whole-cell doses: 2 time since vaccination: up to 4 years vs zero doses	76 (59–86) VE (%) follow-up: 2 to 48 months after vaccination	case-control	Franke et al. 2018 Lancet Glob Health quote In adjusted analyses, the average cumulative 4 year effectiveness for two doses was 76% (95% CI 59-86). abstract, FINDINGS Average cumulative effectiveness with no evidence of decline over follow-up, outside the south Asian settings where the long-term trials were done. Self-reported vaccination.
Culture-confirmed cholera 12 months after a single dose severity: medically attended case definition: Positive stool culture in patients recruited from cholera treatment centres	people aged 12 months and older eligible for the campaign country: Haiti setting: epidemic and newly endemic period: October 2012 to November 2016 n: 178 cases and 706 controls 1-4y5-11y12-17y18-49y50-64y65+	killed bivalent whole-cell oral cholera vaccine platform: killed whole-cell doses: 1 (incomplete regimen) time since vaccination: 12 months vs zero doses	79 (43–93) predicted VE (%) at 12 months follow-up: 12 months after one dose	case-control	Franke et al. 2018 Lancet Glob Health quote In contrast, single-dose effectiveness decreased over time in a log-linear fashion, with a predicted vaccine effectiveness of 79% at the end of 12 months (95% CI 43-93), which declined to zero before the end of the second year. abstract, FINDINGS A model-predicted value from a log-linear decline, not a directly measured interval estimate. The authors report that single-dose effectiveness declined to zero before the end of the second year, which is the key contrast with the flat two-dose curve in the two-dose record. No number is attached to that decline in the abstract, so it is not a separate record.
PCR or culture-confirmed cholera severity: medically attended case definition: Acute watery diarrhoea with stool positive by culture or real-time PCR for the V. cholerae ctxA gene	cases matched to controls by age country: Haiti setting: post-campaign, Euvichol period: September 2018 to March 2020 n: 15 cholera cases and 60 controls All ages	Euvichol platform: killed whole-cell doses: 2 time since vaccination: 10-27 months vs matched community controls without diarrhoea	69 (-71–94) VE (%) follow-up: 10 to 27 months after vaccination	case-control	Matias et al. 2024 Int J Infect Dis quote Adjusted two-dose OCV VE was 69% (95% CI -71 to 94%). abstract, RESULTS Only fifteen cases, so the interval spans zero and this record does not on its own establish Euvichol effectiveness; the authors read it as consistent with Shanchol. Euvichol is the main product in the global stockpile yet has by far the thinnest field evidence.
PCR-confirmed cholera 5 years after a campaign severity: medically attended case definition: Acute watery diarrhoea with stool positive for V. cholerae by PCR, in people eligible for the 2017 campaign	cases frequency-matched with controls by age group country: Haiti setting: outbreak in Mirebalais, 5 years after the campaign period: October 2022 to February 2023 n: 93 cases and 135 controls All ages	Euvichol platform: killed whole-cell doses: at least one dose versus none time since vaccination: 5 years vs people who received no dose	78 (57–89) VE (%) follow-up: 5 years after vaccination	case-control	Ivers et al. 2026 Lancet Reg Health Am quote Receiving Euvichol in 2017 was associated with a 5-year adjusted VE of 78% (95% CI: 57%-89%, p < 0.0001). abstract, FINDINGS The exposure is at least one dose five years after a two-dose campaign, so it does not separate one from two doses. A 5-year estimate this high sits above the pooled meta-analytic four-year figures and rests on self-reported vaccination; treat the level, not just the direction, with caution.
Culture-confirmed cholera, two self-reported doses severity: medically attended case definition: Positive stool culture, compared with community controls and with test-negative controls	cases matched to controls by age group country: Haiti setting: rural cholera treatment centres period: October 2012 to November 2016 n: 181 cholera cases, 157 non-cholera diarrhoea cases, 716 community controls All ages	killed bivalent whole-cell oral cholera vaccine platform: killed whole-cell doses: 2 vs community controls and test-negative controls	72 to 74 VE (%) range across two control groups	case-control	Franke et al. 2017 Vaccine quote VE for self-reported vaccination with two doses was consistent across the two control groups, with statistically significant VE estimates ranging from 72 to 74%. abstract, RESULTS A methods study: the point is that both control types give the same answer, so the Haiti estimates are unlikely to be an artefact of control selection. The same abstract reports bias-indicator estimates well short of the cholera estimates, some statistically significant, which is filed separately as a caution.
Non-cholera diarrhoea (bias indicator, negative control outcome) severity: medically attended case definition: Non-cholera diarrhoea cases compared with community controls	cases matched to controls by age group country: Haiti setting: rural cholera treatment centres period: October 2012 to November 2016 n: 157 non-cholera diarrhoea cases and 625 bias-indicator controls All ages	killed bivalent whole-cell oral cholera vaccine platform: killed whole-cell doses: 2 vs community controls without diarrhoea	19 to 43 apparent VE (%) against non-cholera diarrhoea	case-control	Franke et al. 2017 Vaccine quote Bias-indicator estimates were consistently less than one, with VE estimates ranging from 19 to 43%, some of which were statistically significant. abstract, RESULTS An apparent effect against an outcome the vaccine cannot prevent, i.e. evidence of some bias in the community-control design. The authors judge the bias minimal because test-negative analyses agreed, but this record is the reason the Haiti case-control estimates should not be read as precisely as their intervals suggest.
Cholera during the 2017-2018 Lusaka outbreak severity: medically attended case definition: Cholera cases in a matched case-control study after a mass campaign	cases matched to controls on age and sex country: Zambia setting: peri-urban outbreak response, Lusaka subdistricts period: 2017-2018 n: 79 cases and 316 controls All ages	Euvichol-plus platform: killed whole-cell doses: 2 vs unvaccinated matched controls	81.0 VE (%)	case-control	Sialubanje et al. 2022 BMJ Open quote RESULTS: The AOR vaccine effectiveness for two doses of Euvichol-plus OCV was 81.0% (95% CI 66.0% to 78.0%; p<0.01). abstract, RESULTS The published abstract gives a 95% CI of 66.0% to 78.0%, which does not contain the point estimate of 81.0%; the interval is therefore not recorded here and the discrepancy is flagged in this file. The same abstract reports a lower any-dose estimate, which is filed as its own record.
Cholera during the 2017-2018 Lusaka outbreak, any dose severity: medically attended case definition: Cholera cases in a matched case-control study after a mass campaign	cases matched to controls on age and sex country: Zambia setting: peri-urban outbreak response, Lusaka period: 2017-2018 n: 79 cases and 316 controls All ages	Euvichol-plus platform: killed whole-cell doses: any dose vs unvaccinated matched controls	74.0 (50.0–86.0) VE (%)	case-control	Sialubanje et al. 2022 BMJ Open quote Secondary analysis showed that vaccine effectiveness for any dose was 74.0% (95% CI 50.0% to 86.0%; p<0.01). abstract, RESULTS This secondary analysis has a coherent interval, unlike the two-dose estimate from the same study, so it is the more usable of the two numbers.
Confirmed cholera after a single-dose campaign (matched case-control) severity: medically attended case definition: Confirmed cholera cases versus neighbourhood controls matched by age and sex	matched by age; all ages country: Zambia setting: urban outbreak response, Lusaka period: 2016 n: 66 confirmed cases and 1055 matched controls All ages	oral cholera vaccine used in the single-dose Lusaka campaign platform: killed whole-cell doses: 1 time since vaccination: within months vs unvaccinated neighbourhood controls	88.9 (42.7–97.8) VE (%) follow-up: short term after the campaign	case-control	Ferreras et al. 2020 Epidemiol Infect quote Adjusted vaccine effectiveness of one dose of oral cholera vaccine (OCV) was 88.9% (95% confidence interval (CI) 42.7-97.8) in the MCC study, 80.2% (95% CI: 16.9-95.3) in the TNCC design and 89.4% (95% CI: 64.6-96.9) in the case-cohort study. abstract One of three designs applied to the same outbreak; the test-negative and case-cohort estimates are separate records. The authors conclude most of the protection was the direct effect of the vaccine and that healthcare-seeking bias did not appear to distort the estimates.
Confirmed cholera after a single-dose campaign (test-negative design) severity: medically attended case definition: Confirmed cholera cases versus cases with negative culture and PCR results	all ages country: Zambia setting: urban outbreak response, Lusaka period: 2016 n: 66 confirmed and 145 non-cholera diarrhoea cases All ages	oral cholera vaccine used in the single-dose Lusaka campaign platform: killed whole-cell doses: 1 vs test-negative diarrhoea cases	80.2 (16.9–95.3) VE (%)	test-negative	Ferreras et al. 2020 Epidemiol Infect quote Adjusted vaccine effectiveness of one dose of oral cholera vaccine (OCV) was 88.9% (95% confidence interval (CI) 42.7-97.8) in the MCC study, 80.2% (95% CI: 16.9-95.3) in the TNCC design and 89.4% (95% CI: 64.6-96.9) in the case-cohort study. abstract The test-negative estimate is the lowest of the three designs and has the widest interval, which is what one would expect if community controls carry some bias.
Confirmed cholera after a single-dose campaign (case-cohort) severity: medically attended case definition: Confirmed cholera cases against a randomly selected at-risk cohort	all ages country: Zambia setting: urban outbreak response, Lusaka period: 2016 n: 66 confirmed cases and a cohort of 921 All ages	oral cholera vaccine used in the single-dose Lusaka campaign platform: killed whole-cell doses: 1 vs randomly selected residents of at-risk areas	89.4 (64.6–96.9) VE (%)	cohort	Ferreras et al. 2020 Epidemiol Infect quote Adjusted vaccine effectiveness of one dose of oral cholera vaccine (OCV) was 88.9% (95% confidence interval (CI) 42.7-97.8) in the MCC study, 80.2% (95% CI: 16.9-95.3) in the TNCC design and 89.4% (95% CI: 64.6-96.9) in the case-cohort study. abstract Three designs on one outbreak all give high short-term single-dose protection in an African urban setting, in contrast to the modest single-dose efficacy measured over six months to two years in the Dhaka trial.
Medically attended confirmed cholera 12-17 months after one dose severity: medically attended case definition: Medically attended confirmed cholera at the two cholera treatment facilities in Uvira	age-matched cases and controls, including children vaccinated under 5 years country: Democratic Republic of the Congo setting: urban endemic, high-burden (Uvira) period: October 2021 to March 2022 n: 658 cases and 2274 controls All ages	Euvichol-Plus platform: killed whole-cell doses: 1 time since vaccination: 12-17 months vs age, sex and neighbourhood-matched community controls	52.7 (31.4–67.4) VE (%) follow-up: 12-17 months after vaccination	case-control	Malembaka et al. 2024 Lancet Infect Dis quote The adjusted single-dose vaccine effectiveness was 52·7% (95% CI 31·4 to 67·4) 12-17 months after vaccination and 44·7% (24·8 to 59·4) 24-36 months after vaccination. abstract, FINDINGS The largest single-dose effectiveness study, and the main field evidence for the single-dose policy adopted during the stockpile shortage. Protection in this window was similar in children aged 1-4 years and older people.
Medically attended confirmed cholera 24-36 months after one dose severity: medically attended case definition: Medically attended confirmed cholera in Uvira	age-matched cases and controls country: Democratic Republic of the Congo setting: urban endemic, high-burden (Uvira) period: November 2022 to October 2023 n: 658 cases and 2274 controls All ages	Euvichol-Plus platform: killed whole-cell doses: 1 time since vaccination: 24-36 months vs age, sex and neighbourhood-matched community controls	44.7 (24.8–59.4) VE (%) follow-up: 24-36 months after vaccination	case-control	Malembaka et al. 2024 Lancet Infect Dis quote The adjusted single-dose vaccine effectiveness was 52·7% (95% CI 31·4 to 67·4) 12-17 months after vaccination and 44·7% (24·8 to 59·4) 24-36 months after vaccination. abstract, FINDINGS Substantial protection from one dose persisting into the third year in this setting, which is longer than the Haiti case-control study found for one dose.
Medically attended confirmed cholera in children aged 1-4 years, third year after one dose severity: medically attended case definition: Medically attended confirmed cholera in Uvira	children aged 1-4 years at vaccination country: Democratic Republic of the Congo setting: urban endemic, high-burden (Uvira) period: 24-36 months after the 2020 campaign n: 99 cases were younger than 5 years at vaccination 1-4y	Euvichol-Plus platform: killed whole-cell doses: 1 time since vaccination: 24-36 months vs age, sex and neighbourhood-matched community controls	32.9 (-30.7–65.5) VE (%) follow-up: third year after vaccination	case-control	Malembaka et al. 2024 Lancet Infect Dis quote Although protection in the first 12-17 months after vaccination was similar for children aged 1-4 years and older individuals, the estimate of protection in children aged 1-4 years appeared to wane during the third year after vaccination (adjusted vaccine effectiveness 32·9%, 95% CI -30·7 to 65·5), with CIs spanning the null. abstract, FINDINGS The interval spans the null: single-dose protection in young children appears to wane during the third year. This is the record that argues against relying on one dose for under-5s beyond about two years.
Cholera after a single-dose outbreak campaign severity: medically attended case definition: Suspected cholera classified as cholera positive, against a community cohort	residents of Juba of all ages country: South Sudan setting: urban outbreak response (Juba) period: August to September 2015 n: 34 cholera-positive cases and an 898-person cohort All ages	Shanchol platform: killed whole-cell doses: 1 time since vaccination: short term vs unvaccinated members of the Juba cohort	87.3 (70.2–100.0) VE (%) adjusted follow-up: weeks to months after the campaign	cohort	Azman et al. 2016 Lancet Glob Health quote The unadjusted single-dose vaccine effectiveness was 80·2% (95% CI 61·5-100·0) and after adjusting for potential confounders was 87·3% (70·2-100·0). abstract, FINDINGS A case-cohort study with few cases, and the upper bound reaches unity. The unadjusted estimate is a separate record. This study, with the Zambia ones, is why single-dose reactive campaigns became standard practice despite modest single-dose trial efficacy.
Cholera after a single-dose outbreak campaign, unadjusted severity: medically attended case definition: Suspected cholera classified as cholera positive, against a community cohort	residents of Juba of all ages country: South Sudan setting: urban outbreak response (Juba) period: August to September 2015 n: 34 cholera-positive cases and an 898-person cohort All ages	Shanchol platform: killed whole-cell doses: 1 vs unvaccinated members of the Juba cohort	80.2 (61.5–100.0) VE (%) unadjusted	cohort	Azman et al. 2016 Lancet Glob Health quote The unadjusted single-dose vaccine effectiveness was 80·2% (95% CI 61·5-100·0) and after adjusting for potential confounders was 87·3% (70·2-100·0). abstract, FINDINGS Adjustment moved the estimate up rather than down, which is unusual and worth noting when weighing these small outbreak studies.
Cholera during an outbreak after a mass campaign severity: medically attended case definition: Incidence of cholera compared between vaccine recipients and non-recipients	individuals aged 2 years and older country: Tanzania (Zanzibar) setting: rural and urban high-risk sites period: February 2009 to May 2010 n: 48,178 eligible, 23,921 received two doses 1-4y5-11y12-17y18-49y50-64y65+	killed whole-cell B subunit cholera vaccine (Dukoral) platform: killed whole-cell with B subunit doses: 2 vs non-recipients in the same population	79 (47–92) direct effectiveness (%) follow-up: outbreak within about a year of vaccination	cohort	Khatib et al. 2012 Lancet Infect Dis quote The vaccine conferred 79% (95% CI 47-92) direct protection against cholera in participants who received two doses. abstract, FINDINGS Not randomised: people who chose vaccination may differ from those who did not, though the absence of any effect against non-cholera diarrhoea argues against gross bias. The same study found indirect protection rising with neighbourhood coverage, reported without a single summary figure.
PCR-confirmed cholera among fishermen severity: medically attended case definition: Diarrhoea patients PCR-positive for V. cholerae O1 versus PCR-negative diarrhoea patients	adult fishermen living on the lake sex: men risk group: mobile, hard-to-reach fishermen country: Malawi setting: outbreak response, Lake Chilwa period: 2016 n: 120 fishermen among 145 study participants 18-49y50-64y	Shanchol, second dose self-administered two weeks later platform: killed whole-cell doses: 2, the second taken unsupervised time since vaccination: 3 months vs PCR-negative diarrhoea patients	90.0 (38.8–98.4) VE (%) follow-up: three months	test-negative	Grandesso et al. 2019 Vaccine quote Vaccine effectiveness at three-months was 90.0% [95%CI:38.8;98.4] among fishermen and 83.3% [95%CI: 20.8; 96.5] among all participants in the case-control test-negative design, and 97.5% [95%CI: 90.9;99.3] with the screening method. abstract, RESULTS Tests a delivery strategy as much as a vaccine: the second dose was handed over in a sealed bag to be drunk later. Very wide interval on few cases.
PCR-confirmed cholera among all study participants severity: medically attended case definition: Diarrhoea patients PCR-positive for V. cholerae O1 versus PCR-negative diarrhoea patients	all study participants around the lake country: Malawi setting: outbreak response, Lake Chilwa period: 2016 n: 145 study participants All ages	Shanchol, second dose self-administered platform: killed whole-cell doses: 2, the second taken unsupervised time since vaccination: 3 months vs PCR-negative diarrhoea patients	83.3 (20.8–96.5) VE (%) follow-up: three months	test-negative	Grandesso et al. 2019 Vaccine quote Vaccine effectiveness at three-months was 90.0% [95%CI:38.8;98.4] among fishermen and 83.3% [95%CI: 20.8; 96.5] among all participants in the case-control test-negative design, and 97.5% [95%CI: 90.9;99.3] with the screening method. abstract, RESULTS The same study's screening-method estimate is 97.5% (90.9-99.3), a much narrower interval from a weaker design; the test-negative estimates are the ones to rely on.
Culture-confirmed cholera severe enough to prompt treatment severity: medically attended case definition: Culture-confirmed cholera prompting treatment, versus age and sex matched neighbourhood controls	non-pregnant persons at least two years of age immune status: population with 20 to 30 percent HIV seroprevalence country: Mozambique setting: urban mass immunisation in a high-HIV city (Beira) period: December 2003 to May 2004 n: 43 persons with cholera and 172 controls 1-4y5-11y12-17y18-49y50-64y65+	recombinant cholera-toxin B subunit, killed whole-cell vaccine (rBS-WC, Dukoral) platform: killed whole-cell with recombinant B subunit doses: one or more doses vs age and sex matched neighbourhood controls without treated diarrhoea	78 (39–92) VE (%) follow-up: outbreak within months of the campaign	case-control	Lucas et al. 2005 N Engl J Med quote Receipt of one or more doses of rBS-WC vaccine was associated with 78 percent protection (95 percent confidence interval, 39 to 92 percent; P=0.004). abstract, RESULTS One or more doses, in a setting with high HIV prevalence, and the abstract states the vaccine was equally effective in children under five and older people, which is unusual among these studies. HIV status of individuals was not measured, only city seroprevalence, so this is not an immunocompromised-specific estimate.
Cholera during an El Tor outbreak 3-5 years after mass immunisation severity: medically attended case definition: Cholera cases during the 2003 El Tor outbreak in a case-control study	children and adults immunised in the mass campaign country: Viet Nam setting: urban mass immunisation (Hue) period: outbreak in 2003, vaccination in 1998 and 2000 1-4y5-11y12-17y18-49y50-64y65+	killed whole-cell oral cholera vaccine produced in Viet Nam platform: killed whole-cell doses: 2 time since vaccination: 3-5 years vs unvaccinated residents	50 (9–63) VE (%) follow-up: 3-5 years after vaccination	case-control	Thiem et al. 2006 Vaccine quote The overall vaccine effectiveness 3-5 years after vaccination was 50% (9-63%). abstract A locally produced precursor of Shanchol, and one of the few estimates measured 3 to 5 years out in the field. The lower bound is close to zero.

Gaps

No post-acute sequelae of cholera were found: three PubMed searches for long-term outcomes after cholera (growth faltering, kidney injury, general sequelae) returned nothing cholera-specific. Cholera appears to have no recognised chronic sequelae in the literature searched, but this has not been confirmed from a review.
No safety records: the Cochrane 2024 abstract states no difference in adverse events between vaccine and control groups but gives no number, so it cannot be a record. Vaxchora adverse-event comparisons in the Yellow Book are qualitative only.
No age-stratified case fatality (children under 5 versus adults) was found; the Africhol abstract gives only the proportion of suspected cases under five, and the icddr,b surveillance abstract gives no proportion of severe dehydration by age.
The WHO 2017 cholera vaccine position paper could not be read (IRIS PDF snapshots empty), so the WHO GRADE summary of efficacy is not represented.
No pregnancy-specific efficacy record; the Zanzibar pregnancy paper (PMID 22848772) is about safety and was not compiled.
No immunocompromised or HIV-specific effectiveness estimate was found; the Beira study is a population with high HIV prevalence but reports no HIV-stratified figure.

Flags for review

PMID 36368745 (Zambia, two doses of Euvichol-plus) reports a vaccine effectiveness of 81.0% with a 95% CI of 66.0% to 78.0%, an interval that does not contain its own point estimate. Almost certainly a typographical error in the published abstract. Record cholera-eff-074 therefore carries the point estimate with no interval; a reviewer should check the full text before the number is displayed.
PMID 21412922 (Cochrane 2011) reports second-year efficacy as 62% with a 95% CI of 51% to 62%, an upper bound equal to the point estimate. That estimate is not compiled as a record; the review is also formally superseded by Cochrane 2024 (PMID 38197546) and is kept here only for its first-year and age-stratified figures (cholera-eff-060 to cholera-eff-063).
The eight Cochrane 2024 records (cholera-eff-037 to cholera-eff-044) report vaccine effectiveness as a percentage while the confidence interval is on the risk-ratio scale, so they carry ci_scale=RR. A reader who misses the label will read "37 (0.47-0.85)" as a percentage interval. Verify the rendering wherever this data is published.
Efficacy and effectiveness are deliberately not pooled in this file, because both meta-analyses (PMID 28729167, PMID 40580988) report observational effectiveness well above randomised efficacy at the same time points. The case-control estimates, most of which rest on self-reported vaccination, should not be presented as interchangeable with trial figures.
The two bias-indicator records (cholera-eff-067 and cholera-eff-073) are apparent effectiveness against non-cholera diarrhoea, an outcome these vaccines cannot prevent. They are negative-control checks, not benefits, and must never be rendered as protection. cholera-eff-073 shows a statistically significant apparent effect, i.e. measurable bias in the community-control design used across the Haiti studies.
The under-5 age pattern is the most consistent finding in this file and the most likely to be lost in a summary: two-dose efficacy in children under five is about half that in older people (cholera-eff-047 versus cholera-eff-048), and single-dose protection in under-5s was not demonstrated at all in the Dhaka trial (cholera-eff-016, cholera-eff-017) and waned in the third year in the DRC (cholera-eff-081). Any headline figure for these vaccines needs that qualifier attached.
cholera-bur-006 (case fatality up to 50% untreated) is a stated upper bound in a CDC chapter, not a measured cohort value, and must not be shown as a typical risk. The measured outbreak figures are 0.22% in Yemen, 2.3% in national Haiti surveillance and up to 15.2% in a survey of remote Haitian districts with poor treatment access.
The Haiti burden records use three incompatible denominators: nationally reported cases, self-reported watery diarrhoea in a household survey of four remote districts, and crude all-cause mortality per 1,000 person-years. They must not be combined or multiplied.
cholera-bur-026 (severe dehydration among Yemeni cholera inpatients) has hospitalisations as its denominator, not infections. It must not be read next to the proportion of infections that become severe (cholera-bur-008, cholera-bur-009), nor multiplied by it.
The two challenge-study products (cholera-eff-033 to cholera-eff-036, Vaxchora / CVD 103-HgR) are a live attenuated single-dose travel vaccine measured by experimental challenge in cholera-naive US adults. Their high efficacy figures are not comparable with the field estimates for the killed whole-cell vaccines used in endemic countries, and no field effectiveness data for this product were found.
The WHO 2017 cholera vaccine position paper could not be read: the iris.who.int PDF snapshot returned six characters on two attempts, and the landing page carries no evidence text. Many other iris-who-int entries already in sources/web are the same six-character stubs, so websource.py appears unable to retrieve IRIS PDFs at all. WHO's own GRADE assessment is therefore missing from this file.
Shanchol, the product behind most of the trial evidence in this file, is no longer produced according to the WHO fact sheet, while Euvichol-Plus and Euvichol-S, which carry the global stockpile, have only a handful of small field studies (cholera-eff-070, cholera-eff-071, cholera-eff-074, cholera-eff-075, cholera-eff-079 to cholera-eff-081) and no randomised trial. Cochrane 2024 states it is reasonable to apply the Shanchol results to them on the basis of comparable vibriocidal responses; that bridging assumption underlies most current policy and should be stated on the page rather than implied.

Search log (36 searches)

oral cholera vaccine Kolkata randomized trial efficacy five years · PubMed → Found PMID 40580988 (Xu 2025 updated kOCV meta-analysis).
Bhattacharya oral cholera vaccine Kolkata 5 year efficacy cluster randomised · PubMed → Found PMIDs 24140390 (5-year), 19819004 (2-year interim), 22028938 (3-year) Kolkata Shanchol RCT reports.
single dose oral cholera vaccine Bangladesh efficacy randomized · PubMed → Found PMIDs 27144848 (Qadri 2016 NEJM, 6 months) and 29550406 (Qadri 2018, 2 years).
oral cholera vaccine effectiveness Haiti case-control · PubMed → Found PMIDs 25701994, 30103980, 38000510, 42257677, 28916247 (Haiti case-control series 2015-2026).
oral cholera vaccine effectiveness Guinea Conakry · PubMed → Found PMID 24869721 (Luquero 2014 NEJM).
oral cholera vaccine effectiveness Zambia Lusaka single dose · PubMed → Found PMIDs 36368745 (two-dose Euvichol-plus 2017/18), 32167038 (one-dose 2016, three designs), 29403111 (implementation, no VE).
Clemens oral cholera vaccine Bangladesh field trial three years follow-up B subunit · PubMed → Found PMIDs 2873397 (6 months), 3392421 (1 year), 1967730 (3 years), 8852414 (5 years) of the 1985 Matlab BS-WC/WC trial.
Vaxchora CVD 103-HgR challenge study efficacy · PubMed → Found PMID 10569747 (Tacket 1999 challenge at 3 months).
Chen CVD 103-HgR PXVX0200 challenge 10 days 90 days randomized · PubMed → Found PMID 27001804 (Chen 2016 challenge at 10 days and 3 months).
Cochrane oral cholera vaccines preventing cholera Sinclair · PubMed → Found PMID 21412922 (Sinclair 2011, superseded).
Saif-Ur-Rahman oral killed cholera vaccines Cochrane 2024 · PubMed → Found PMID 38197546 (Cochrane 2024 update).
oral cholera vaccine meta-analysis efficacy effectiveness duration Bi 2017 · PubMed → Found PMID 28729167 (Bi 2017 Lancet Infect Dis).
herd protection oral cholera vaccine Bangladesh Ali Lancet · PubMed → Found PMID 15993232 (Ali 2005 reanalysis).
ring vaccination strategy cholera re-analysis cluster-randomized Ali PLoS Med · PubMed → Found PMID 27622507 (Ali 2016 Kolkata ring reanalysis).
ring vaccination oral cholera vaccine Bangladesh · PubMed → Found PMID 29174695 (Ali 2018 vaccine-probe transmission rings); no trial of prospective ring vaccination found.
global burden of cholera endemic countries Ali 2015 · PubMed → Found PMID 26043000.
cholera case fatality rate Yemen outbreak 2017 · PubMed → Found PMIDs 29731398 (Camacho 2018 surveillance analysis) and 33489949 (Alassar 2020 inpatient cohort).
cholera outbreak Haiti 2010 case fatality rate · PubMed → Found PMIDs 21150867 (MMWR 2010), 26886511 (Luquero 2016 mortality survey), 25811860 (Page 2015 rural survey).
cholera children under five Bangladesh severe dehydration · PubMed → Found PMID 35204858 (icddr,b malnourished vs non-malnourished children; no usable numeric proportion in the abstract).
cholera case fatality rate children under 5 Africa surveillance · PubMed → Found PMID 27186885 (Africhol multi-country surveillance).
cholera case fatality rate reported WHO annual global 2023 · PubMed → Found PMID 40775053 (Perez-Saez 2025 Africa incidence mapping).
oral cholera vaccine effectiveness Zanzibar Khatib · PubMed → Found PMID 22954655.
oral cholera vaccine effectiveness Malawi Lake Chilwa · PubMed → Found PMID 31133470.
oral cholera vaccine Mozambique Beira effectiveness · PubMed → Found PMID 15728808.
oral cholera vaccine Vietnam Hue effectiveness · PubMed → Found PMIDs 9014909 (1997 field trial) and 16580760 (3-5 year effectiveness).
Sanchez oral cholera vaccine Peruvian military recruits efficacy · PubMed → Found PMID 7967990.
inactivated oral cholera vaccine Dhaka cluster-randomised open-label trial behavioural change · PubMed → Found PMID 26164097 (Qadri 2015 Lancet).
oral cholera vaccine effectiveness Democratic Republic of Congo case-control Uvira · PubMed → Found PMID 38246191 (Malembaka 2024 single dose).
oral cholera vaccine effectiveness South Sudan Juba Shanchol · PubMed → Found PMID 27765293 (Azman 2016 case-cohort).
cholera long-term sequelae after infection growth malnutrition children · PubMed → No results.
cholera acute kidney injury outcome children hospitalized · PubMed → One unrelated AKI aetiology paper; nothing cholera-specific.
growth faltering after cholera infection children follow-up · PubMed → No results.
cholera deaths global burden disease estimates GBD · PubMed → No cholera-specific GBD paper surfaced; only unrelated GBD papers.
WHO cholera fact sheet · WHO website → Snapshotted as web who-int-3a8bd5a00b.
Cholera vaccines WHO position paper August 2017 · WHO website and IRIS → Landing page snapshotted (who-int-f550f4ea52) but holds no evidence text; the IRIS PDF returned 6 characters on two attempts.
CDC cholera about page and Yellow Book cholera chapter · CDC website → Snapshotted as cdc-gov-b8e4bdb00b and cdc-gov-8637982d0a.