Varicella (Chickenpox) vaccine side effects (Varivax): VAERS data, trials and schedule
This page answers “chickenpox vaccine side effects” with sourced pharmacovigilance data — MMRV febrile-seizure context and VAERS breakdowns. Counts are database reports, not proven vaccine-caused injury rates.
How to read database counts: Pharmacovigilance systems (VAERS, EudraVigilance, Yellow Card, VigiBase, Lareb, DAEN) collect spontaneous, unverified reports. A report is not a confirmed adverse event and does not prove the vaccine caused the outcome. Under-reporting, stimulated reporting, and missing denominators limit rate interpretation. Compare with trials and epidemiological studies on each page before drawing conclusions.
Gold Standard EO (Aug 10, 2026)Federal recommendation status: Recommended for all children
The August 10, 2026 Executive Order on Gold Standard Childhood Vaccine Recommendations places varicella in the Recommended for all children category. The EO also expresses a preference, to the maximum extent feasible, for administering all childhood immunizations at separate medical visits.
This page summarizes published data for varicella vaccine (Varivax®) and the MMRV combination vaccine (ProQuad®). The U.S. introduced universal 1-dose varicella vaccination in 1995 and added a 2nd dose in 2006 due to breakthrough disease. MMRV was licensed in 2005. An important safety finding for MMRV (but not MMR + varicella given separately) is an elevated febrile seizure risk in the 5–12 day window. Data are presented without interpretive language that implies the vaccine is "safe" or "unsafe."
Evidence state
For each outcome: the specific question, what controlled studies found, and how certain that evidence is on the GRADE scale (high, moderate, low, very low). Ratings are editorial judgments by the site applying GRADE to the studies in the table below — observational evidence starts at low and is rated up for large, consistent effects or a dose/age gradient, and down for inconsistency or imprecision (Methods). Where an effect is confined to a subgroup (for example young males), the question says so. "Not searched" means no controlled study has been compiled here yet; it is not a finding that the outcome is rare or caused by the vaccine.
Outcome & question
Finding & certainty
Why this rating
Herpes zoster
Varicella vaccine in children
lower risk of shingles in vaccinated children than after natural chickenpox Moderate certainty
Start low; +1 large protective effect: incidence 38 vs 170 per 100,000 person-years in vaccinated vs unvaccinated children (ratio 0.22) in the largest cohort, RR 0.61 in a second cohort, and a 69% population decline in an ecological study. Studies: Weinmann 2019, Baxter 2013, Civen 2016.See table
Immune thrombocytopenia
Varicella vaccine, adolescents
inconclusive Very low certainty
Single study with too few events. Studies: O'Leary 2012.See table
Anaphylaxis
Not searched
No controlled-study result is compiled for this outcome yet.
Myocarditis or pericarditis
Not searched
No controlled-study result is compiled for this outcome yet.
Guillain-Barré syndrome
Not searched
No controlled-study result is compiled for this outcome yet.
Febrile seizure
Not searched
No controlled-study result is compiled for this outcome yet.
Type 1 diabetes
Not searched
No controlled-study result is compiled for this outcome yet.
Encephalitis / encephalopathy
Not searched
No controlled-study result is compiled for this outcome yet.
1. Basic Information
Disease Protected Against
Varicella (Chickenpox) is caused by varicella-zoster virus (VZV). Before vaccination, varicella caused ~4 million cases, ~10,500–13,500 hospitalizations, and ~100–150 deaths annually in the U.S. Complications include bacterial superinfection (primarily Group A Strep), pneumonia, encephalitis, and congenital varicella syndrome. VZV establishes latency in dorsal root ganglia; reactivation later in life causes herpes zoster (shingles).
CDC Schedule (U.S., 2025)
Dose
Age
Product
Dose 1
12–15 months
Varivax (standalone) or ProQuad (MMRV)
Dose 2
4–6 years
Varivax or ProQuad. Minimum interval: 3 months between doses.
Source: CDC ACIP, 2025 schedule. ACIP recommends MMR + varicella separately for dose 1 in children 12–47 months due to MMRV febrile seizure risk; MMRV may be used for dose 2 or for dose 1 in children ≥48 months.
Licensed Varicella (Chickenpox) vaccine products
Each product has its own page with package-insert ingredients, side-effect data, lot lookup and comparisons with the other brands.
live attenuated; intramuscular_or_subcutaneous; no adjuvant
Ingredients (Package Insert)
Structured composition for 1 branded product covered on this page,
taken from FDA-approved package inserts (DailyMed / manufacturer prescribing information).
Lists are per product — formulations differ by manufacturer and presentation.
Click an ingredient name to open its safety-context page when available.
Live attenuatedIM or SCNo preservative (typical single-dose)GelatinNeomycin
VarivaxMerck Sharp & Dohme LLC · Live attenuated
Delivery
Route: IM or SC
Form: Lyophilized powder (reconstitute)
Dose volume: 0.5 mL
Presentation: single-dose vial + sterile diluent
Encapsulation / delivery vehicle
None (no nanoparticle/VLP encapsulation system)
Antigens
Antigen
Type
Amount / dose
Varicella-zoster virus (live, attenuated)
Strain: Oka/Merck · System: MRC-5 cells
Live attenuated virus
≥1350 PFU per 0.5 mL
Adjuvants
None listed on the package insert for this product (common for live attenuated and some inactivated whole-virus vaccines).
Preservatives
None — Single-dose presentation; label states no preservative.
Ingredient lists are sourced from official package inserts for the specific brands named above.
Formulations can change between lots and over time — verify against the current label before any clinical decision.
Presence of a substance does not by itself indicate harm; toxicology is dose-, route-, and context-dependent.
Browse the full ingredient database:
Vaccine Ingredients index.
Causality assessment & potential mechanisms
Conditions below combine WHO-style causality levels with potential biological mechanisms
from the site mechanism catalog
(ae_mechanisms_catalog.json).
HRSA VICP table listing (where shown) indicates a compensable temporal association under U.S. program rules —
not automatic proof of causation for every case. Mechanisms are hypothesis-level pathways with graded evidence.
Pre-existing or newly formed IgE against vaccine antigens or excipients (e.g., gelatin, egg proteins, PEG, polysorbate) triggers mast-cell and basophil degranulation with systemic mediator release.
Vaccine-strain varicella (disseminated)HRSA table
0–42 days
Very likely / Probable
Evidence: High
Uncontrolled live attenuated vaccine replication (primary · live_replication)
In immunocompromised or otherwise susceptible hosts, live attenuated vaccine strains can replicate beyond the intended limited infection, causing disseminated disease or organ-specific infection.
Herpes zoster (vaccine strain)HRSA table
0–365 days
Possible
Evidence: Moderate
Uncontrolled live attenuated vaccine replication (primary · live_replication)
In immunocompromised or otherwise susceptible hosts, live attenuated vaccine strains can replicate beyond the intended limited infection, causing disseminated disease or organ-specific infection.
Vaccine-induced fever lowers seizure threshold in susceptible young children; measles-containing vaccines show a well-documented risk window roughly 7–14 days post-dose.
Framework: WHO causality + HRSA VICP (where applicable) + AE mechanism catalog.
Last updated: 2026-07-18.
Schema: schemas/vaccine_injury_table.schema.json
· Mechanisms: schemas/ae_mechanism.schema.json.
Not medical or legal advice.
2. Pre-Licensure Clinical Trial Data
Licensure trial design (ICAN / OpenVAERS)
The table below reproduces ICAN’s No Placebo Table rows for U.S. childhood-schedule products relevant to this page — including the control/comparator used in FDA licensing trials (not always saline placebo). OSMF presents this for transparency; it is not an endorsement of ICAN interpretations.
Vaccine
Brand
Manufacturer
Doses (schedule)
Ages injected
Control / comparator
Placebo
Safety review window
VAR
Varivax
Merck
2
12M 4Y
45 mg of neomycin per milliliter
No
70 days
Source: OpenVAERS — No Placebo Table · ICAN original PDF
· Attribution: Informed Consent Action Network (ICAN) via OpenVAERS
· Last fetched: 2026-07-16.
For many trials listing '6 months' safety review, ICAN notes review was typically ~30 days post-injection with a phone call at 6 months.
Varivax was licensed in 1995 based on clinical trials in ~11,000 children and adults. The pivotal efficacy trial enrolled ~1,000 children. ProQuad (MMRV) was licensed in 2005 based on trials in ~6,000 children.
Injection site reactions (~20–30%), fever (~10–15%), varicella-like rash (~3–5%, may be infectious)
MMRV Febrile Seizure Finding
The MMRV pre-licensure trials observed a higher rate of fever (38–40%) and a numerically higher rate of febrile seizures compared to MMR + varicella given separately. The febrile seizure risk was confirmed post-licensure in VSD studies: ~1 additional febrile seizure per 1,250 MMRV doses compared to MMR + varicella given separately, in the 5–12 day post-vaccination window. This led to the ACIP preference for separate MMR + varicella for dose 1.
3. Post-Licensure Safety Data
Varicella vaccine has >30 years of post-licensure safety data. Key VSD findings:
MMRV febrile seizures: ~1 per 1,250 doses vs. ~1 per 2,500 for MMR + varicella separately (5–12 day window). ACIP preference for separate administration for dose 1 under age 4.
Herpes zoster (shingles) from vaccine strain: Documented in vaccinated children and adults; rate is lower than after wild-type VZV infection. Estimated at ~18–26 per 100,000 person-years in vaccinated children vs. ~74 per 100,000 after wild-type infection.
Vaccine-strain transmission: Occasional transmission of vaccine-strain VZV from a vaccinated person who develops a rash to susceptible contacts. Rare; mostly from immunocompromised vaccinees. No documented transmission from vaccinated persons without a rash.
ITP: MMRV and MMR + varicella both associated with a small ITP risk (attributable primarily to the MMR component — see MMR page).
⚠ Critical Caveat
VAERS data represent unverified reports. A report to VAERS does not mean the vaccine caused the event.
VAERS reports per million doses
U.S. VAERS reports for vaccinations given 2006–2024, divided by the 206 million doses distributed in the same years (HRSA, from CDC data).
All reports
372
per million doses (370–375) · 76,697 reports
Serious reports
14.1
per million doses · 2,894 reports (death, life-threatening, hospitalised or disabled)
Reports with a death
0.84
per million doses · 173 reports
These are reporting rates: they mix real reactions, coincidental events and reports of conditions that would have happened anyway, and they depend on how actively each vaccine is watched. Doses are distributed, not administered. Combination vaccines count toward each component in both numerator and denominator. Compare with the observed-vs-expected analysis and the controlled studies above. Data: vaers_reporting_rates.json.
All vaccines, per million doses
Vaccine
All
Serious
Death
pcv
266
28.1
3.23
rotavirus
157
27.9
4.08
hpv
335
25.3
2.00
hib
126
19.7
3.25
polio
152
17.6
2.77
mmr
320
15.3
0.94
varicella
372
14.1
0.84
hepatitis-b
110
12.7
2.15
meningococcal
214
11.8
0.70
dtap
132
11.2
1.31
hepatitis-a
152
8.5
0.58
influenza
68
5.4
0.48
What controlled safety studies found
Unlike VAERS counts, these studies compare vaccinated people with a control group or control time window, so they can estimate whether a risk is raised and by how much. 6 results for varicella vaccines: 1 found an increased risk of a specific outcome, 4 found no increased risk.
Outcome
Design & population
Estimate (95% CI)
Excess per million doses
Finding
Source
Disseminated Oka VZV; vaccine-strain reactivation (incl. with meningitis/encephalitis)
Varicella (Oka strain)
expert causality review (IOM 2011) General (mostly immunodeficient)
—
—
increased risk
Institute of Medicine (Stratton K et al., eds.), 2011, Adverse Effects of Vaccines: Evidence and Causality, National Academies Press doi:10.17226/13164
Herpes zoster in vaccinated cohort vs prevaccine-era unvaccinated children
Varicella vaccine (Varivax)
prospective cohort (KPNC, 14 y) Children vaccinated in 2nd year of life 1995, US (7585)
Bars are drawn to scale within each comparison. Disease risks are per case of the disease; vaccine risks are the excess above background per dose, from controlled studies. How likely someone is to catch the disease, without vaccination, decides how these weigh up for an individual.
No single study measured both risks in the same population for this vaccine, so no side-by-side ratio is shown; the two lists below come from different studies, eras and populations.
Serious outcomes of the disease (per million cases)
Days from vaccination to onset in U.S. VAERS reports (0–180 days). A causal reaction usually starts inside a characteristic window; but people also report what happens soon after a shot, so each event is compared with all other reports for this vaccine. The Weibull shape measures bunching (below 1 = most onsets early).
Event
Reports
Median days
In risk window
Shape (95% CI) vs others
Reading
Seizure (any)
2,507
2
94% (others 93%)
0.77 (0.74–0.80) vs 0.64
spread later than other reports
Syncope
1,193
0
95% (others 66%)
0.70 (0.65–0.81) vs 0.64
same timing as other reports
Febrile seizure
1,065
4
95% (others 93%)
0.99 (0.95–1.05) vs 0.64
spread later than other reports
Herpes zoster
643
25
49% (others 52%)
0.56 (0.52–0.60) vs 0.64
clusters earlier than other reports
Anaphylaxis
228
0
96% (others 66%)
1.01 (0.87–1.25) vs 0.64
spread later than other reports
Immune thrombocytopenia
155
15
93% (others 52%)
1.24 (1.06–1.65) vs 0.64
spread later than other reports
ADEM / encephalitis
110
11
85% (others 52%)
0.86 (0.76–1.03) vs 0.64
spread later than other reports
Bell's palsy / facial paralysis
55
2
78% (others 52%)
0.85 (0.77–1.00) vs 0.64
spread later than other reports
Guillain-Barré syndrome
53
13
85% (others 52%)
0.97 (0.81–1.23) vs 0.64
spread later than other reports
Transverse myelitis
30
16.5
77% (others 52%)
0.96 (0.79–1.27) vs 0.64
spread later than other reports
Myocarditis / pericarditis
25
5
56% (others 82%)
1.15 (0.94–1.62) vs 0.64
spread later than other reports
Timing alone cannot establish causation; it can make it more or less plausible. *Fitted on a random sample of 5,000 of these reports. Data: vaers_onset.json.
VAERS Reporting Data — Halma & Varon (2025), DARE-SAFE
The DARE-SAFE paper (Halma & Varon, Pharmacoepidemiology 2025, CC BY 4.0) analyzed VAERS reports for vaccines administered in the United States from 2006–2022. The following data are extracted from Table 1 of that paper for this vaccine (Varicella standalone (Varivax); excludes MMRV (MMR-Varicella combination, which had 15,668 reports / 20 deaths / 42.9M doses / 0.0466 death rate)):
Metric
Value
U.S. doses administered (2006–2022)
143,906,028
Total VAERS AE reports
48,863
AE reporting rate (per 100,000 doses)
34.0
Total death reports
84
Death reporting rate (per 100,000 doses)
0.0584
AE-to-Death ratio
582:1
Source: Halma, M.; Varon, J. DARE-SAFE. Pharmacoepidemiology. 2025. DOI: 10.3390/pharma4020007. CC BY 4.0. Data from Table 1.
📚 Important Interpretive Caveats (from the paper itself)
Reporting rate ≠ incidence rate. VAERS is a passive, unverified system. A report means someone submitted a claim of temporal association, not a confirmed causal event. The paper is explicit that causality cannot be inferred from these numbers alone.
Reporting behavior is not uniform. More serious, unusual, or media-salient events are reported at much higher rates than mild ones. Products receiving more public, media, legal, and clinical attention (particularly COVID-19 vaccines, which also benefited from V-safe active-surveillance prompts and CICP compensation pathways) generate more reports per dose regardless of true risk.
Age and comorbidity confounding is not adjusted. COVID-19 vaccines were disproportionately administered to elderly and comorbid populations (nursing homes, 65+, high-risk groups in early 2021) with much higher background all-cause mortality than the general child/working-age population. Some fraction of temporally-associated deaths would occur regardless of vaccination, and the paper does not perform a background-rate comparison.
Stimulated reporting is a known, documented phenomenon. Media coverage, plaintiff attorney solicitation, and advocacy campaigns — all independently inflate VAERS reporting propensity. The paper cites this literature but does not correct for it.
Small-denominator rows are unreliable. Rates computed from small denominators (e.g., monovalent measles, DT, mumps, rubella) have enormous statistical uncertainty and should not be compared to vaccines with hundreds of millions of administered doses without noting the wide confidence intervals.
Source: Halma, M.; Varon, J. DARE-SAFE: Denominator-Adjusted Rate Estimates of Substance Adverse Events Frequency Evaluation in Pharmaceuticals and Vaccines. Pharmacoepidemiology. 2025, 4, 7. DOI: 10.3390/pharma4020007. CC BY 4.0.
Passive Surveillance: AE Type Breakdown (Multi-System)
Side-by-side view of U.S. VAERS, Health Canada Canada Vigilance, Japan JADER (PMDA), EU EudraVigilance, and live-scraped international systems via SurVigilance (VigiAccess, Lareb, DAEN, DMA, Medsafe). SurVigilance panels show MedDRA PT mention totals (not individual-case counts). Category assignment uses keyword matching — approximate, not official SOC coding. VAERS files on this site are built from the public VAERS download. FAERS figures use the public quarterly FAERS files. Counts are mentions or reports, not incidence.
VAERS (United States)
Canada Vigilance (Canada)
JADER (PMDA, Japan)
EudraVigilance (EU)
No matching vaccine cases in the current EudraVigilance DAP export.
This system’s totals are not in this panel. Published counts, when this site has them, are in the surveillance section.
DMA (Denmark)
Denmark DMA interactive ADR search is currently offline (Danish Medicines Agency IT transition; public overviews frozen at 12 Mar 2024). Live product PT tables cannot be retrieved until DKMA restores the search. See DKMA notice. Denmark continues to report into EU EudraVigilance (panel above).
Medsafe (New Zealand)
VAERS (U.S., 2006–2024): 500,832 symptom mentions (174.01/100k doses). Largest share: Other / Unclassified (22%), Injection-site / Local reaction (21%), General / Systemic (non-local) (18%). Canada Vigilance (CV Online extract): 11,067 reaction mentions in 3,417 unique reports (64.0% serious (2,186 of 3,417 reports)). Largest share: General / Systemic (non-local) (17%), Injection-site / Local reaction (17%), Neurological (10%). JADER (PMDA public CSV extract): 1,313 reaction mentions in 666 unique reports (8.1% serious (54 of 666 reports)). Largest share: Other / Unclassified (35%), Neurological (18%), General / Systemic (non-local) (13%). VigiAccess (WHO): 1,395 reaction-term mentions · search: varicella. Largest share: Gastrointestinal (26%), Dermatological (non-injection-site) (18%), Other / Unclassified (12%). Lareb (Netherlands): 80 reaction-term mentions · search: Varicella vaccine. Largest share: General / Systemic (non-local) (22%), Other / Unclassified (16%), Injection-site / Local reaction (15%). Medsafe (New Zealand): 569 reaction-term mentions · search: varicella. Largest share: Injection-site / Local reaction (23%), General / Systemic (non-local) (21%), Other / Unclassified (17%). Cross-database note: All systems are passive and unverified; reporting rates are not directly comparable across countries (different populations, reporting incentives, and lack of dose denominators for Canada/Japan/EU). top VAERS: Other / Unclassified; top Canada Vigilance: General / Systemic (non-local); top JADER: Other / Unclassified. SurVigilance note: VigiAccess, Lareb, DAEN, DMA, and Medsafe counts are live-scraped MedDRA PT mention totals (not deduplicated individual cases). Data via SurVigilance (GPL-3.0; pip install SurVigilance). Category assignment uses keyword matching on reported reaction terms — approximate and exploratory. Neither database establishes causality.
Pharmacovigilance Lot Signal Detection — Hypothesis-Generating Only
Multi-system context below. VAERS (U.S.) supports lot-level volume z-scores and seriousness flags by product and lot (2006–2024). Each lot links to a summary with report count, seriousness %, adverse-event pie chart, U.S. state map, and timeline. A signal flag means a statistical threshold was exceeded — not that a lot is unsafe. Full dashboard →
VAERS flags:VOL high report volume (z ≥ 3) ·
BURST clustered in <90 days ·
SER serious reports >50%.
Lot numbers are voluntary/incomplete in VAERS. Location data is U.S. state only (no postal codes in the public extract).
VAERS (United States) — all lots by product
57,254 reports with usable lot across 4,317 lots · 511 flagged
Loading lot tables…
Other Pharmacovigilance Systems
Lot-level analysis is only possible where reporters supply batch/lot numbers in the public extract. Canada Vigilance, JADER (PMDA, Japan), and most other national systems publish product-level spontaneous reports without lot fields.
Canada Vigilance (Health Canada)
3,417 unique reports · 11,067 reaction mentions · 64.0% serious (2,186 of 3,417 reports). Top categories: General / Systemic (non-local) (17%), Injection-site / Local reaction (17%), Neurological (10%).
Canada Vigilance spontaneous reports are unverified temporal associations. The public CV Online data extract does not include lot or batch numbers, so lot-level signal detection is not possible for this system — only product-level reaction patterns are shown here. No Canadian dose denominators are available. Extract 2026-03-31.
666 unique reports · 1,313 reaction mentions · 8.1% serious (54 of 666 reports). Top categories: Other / Unclassified (35%), Neurological (18%), General / Systemic (non-local) (13%).
JADER (Japanese Adverse Drug Event Report database) spontaneous reports are unverified temporal associations; PMDA has not assessed causality per case. The public CSV extract does not include lot or batch numbers, so lot-level signal detection is not possible — only product-level reaction patterns are shown here. Reaction terms in source data use MedDRA/J Preferred Terms. JADER CSV extract pmdacasereport202606 (2026-06). JADER reference (PDF)
Active Pharmacovigilance (Defined-Population Surveillance)
Curated findings for Varicella (Varivax) / context with MMRV from active systems (not VAERS). Page inventory last reviewed: 2026-07-10.
ⓘ Active vs. passive — why this pane is separate
The VAERS / multi-system charts above are passive surveillance: spontaneous, unverified reports without a fixed denominator.
Active surveillance starts from a defined, enumerated population (EHR/claims or structured post-vaccination surveys), applies pre-specified statistical tests, and asks whether an outcome occurs
more often than expected in a risk window versus a comparison window or group.
These are not two flavors of the same evidence — active findings are the harder tier that can confirm, refute, or leave under investigation a signal first hinted in passive data.
Do not add VAERS report counts to active incidence rates.
○ No signal detected◐ Signal under investigation◑ Investigated — not confirmed● Signal confirmed (true association)– Not currently under active surveillance
CDC Vaccine Safety Datalink (VSD)
Outcome: Febrile seizures (especially MMRV first dose) and other pre-specified outcomes
Tier 2● Signal confirmed (true association)
When varicella is combined as MMRV for the first toddler dose, VSD confirmed higher febrile-seizure risk versus separate injections. Standalone varicella vaccine does not drive that specific combination finding; see MMR page for MMRV detail.
Population
Toddlers receiving varicella-containing vaccines
Risk interval
5–12 days for febrile seizure analyses with measles-containing vaccines
Comparison
Separate MMR + varicella
Evaluation period
Post-licensure combination era
Method
RCA and observational studies (including MMRV combination analyses)
Related passive AE category on this page: Neurological (see multi-system charts above — not additive with active rates).
Update cadence: Tier 1: check AusVaxSafety monthly when public pages update. Tier 2/3: quarterly review around ACIP meetings and PubMed/MMWR; set lastReviewed per record.
Source tiers: Tier 1 = public near-real-time dashboards (e.g. AusVaxSafety);
Tier 2 = VSD / Sentinel / PRAC-type findings released via ACIP slides, MMWR, or papers (no public VSD raw dashboard);
Tier 3 = regulator label/safety communications.
Detecting a signal and later classifying it as not confirmed is normal system behavior — not an anomaly to hide or amplify.
4. Documented Adverse Events
Rank-aggregated VAERS signal detection (rankv)
The table below lists vaccine–event pairs that were detected as disproportionality signals by all four base methods used in rankv (GPS, PRR, ROR, BCPNN) on multi-decade VAERS data, then ordered by rank aggregation (Borda average rank; related to the Spearman/GA top-list approach in the rankv paper).
Data: ~30 years of public VAERS (rankv processed tables).
Origin: precisionFDA “Gaining New Insights by Detecting Adverse Event Anomalies” challenge solution.
Caveat: Disproportionality signals are statistical associations in spontaneous reports. They do not establish causality, incidence, or product defect. Many top pairs reflect administration/product-use coding rather than clinical injury.
Varicella-like rash: 3–5% (mild; may be infectious). Strong
Febrile seizures (MMRV): ~1 per 1,250 doses in the 5–12 day window. Strong
Herpes zoster (vaccine strain): 18–26 per 100,000 person-years; lower than after wild-type infection. Strong
▶ No Causal Association
Autism: No association. MMRV contains the same MMR components studied extensively for autism (see MMR page). No Association
5. Disease Prevention Benefits
Metric
Pre-Vaccine Era (~1990–1994)
Post-Vaccine Era (2-dose, ~2010+)
Varicella cases (annual)
~4 million
>97% reduction; varicella is no longer endemic in the U.S.
Hospitalizations (annual)
~10,500–13,500
>90% reduction; almost exclusively unvaccinated or immunocompromised
Deaths (annual)
~100–150
<10/year
Herpes zoster in children
~74 per 100,000
~18–26 per 100,000 (vaccine-strain); overall pediatric zoster has declined
Source: CDC Pink Book; MMWR. The introduction of a second dose in 2006 effectively addressed breakthrough varicella observed with the 1-dose schedule. Herd immunity has been observed.
Disease Burden Over Time
Reported U.S. disease burden by year. The dashed vertical line marks vaccine introduction. Hover or tap data points for values; use arrow keys when a chart has focus.
ⓘ About these charts: These are accessible SVG line charts with keyboard navigation, hover tooltips, and an underlying data table (expand below). The dashed vertical line marks the year of vaccine introduction. Reported cases undercount true incidence; case definitions, reporting practices, and diagnostic methods have changed over time. See Section 5 for additional context and pre-vs-post era comparisons.
7. Evidence Summary
Varicella vaccine has >30 years of post-licensure data. The safety profile is well-characterized. The primary safety concern is the MMRV-associated febrile seizure risk, which is product-specific and mitigated by ACIP's preference for separate MMR + varicella administration for dose 1. Breakthrough varicella with the 1-dose schedule was addressed by the 2006 2-dose recommendation. Long-term data indicate that vaccine-strain zoster is less common than zoster after wild-type infection.
8. International Surveillance & Global Data
Quick links to public pharmacovigilance databases and trial registries relevant to Varicella Vaccine. Reporting counts do not establish causality.
Note: Spontaneous reports are unverified observations. Compare with epidemiological studies in Sections 3–6 before drawing conclusions.
9. Curated Adverse Event Literature
Curated peer-reviewed literature linking specific adverse events to Varicella (Chickenpox) Vaccine. Each entry is a case report, case series, or related safety publication identified via PubMed. Expand Search PubMed for additional literature below to run custom queries.
Disclaimer: Published reports describe observations and associations; they do not establish population incidence or causality.
Common questions
How long do Varicella vaccine side effects last?
Most reported Varicella vaccine reactions are short-lived: injection-site soreness, tiredness, and low-grade fever that typically begin within a day or two and resolve within a few days. Longer-lasting or more serious events are rarer and are the ones tracked in the post-licensure surveillance and documented adverse-event sections of this page, with report counts that are not incidence rates. Anything severe or persisting beyond a week warrants medical review.
Is the Varicella vaccine given to adults, and are side effects different in adults?
Whether the Varicella vaccine is recommended for adults depends on the vaccine and the person's risk factors; the schedule and product sections above describe the licensed indications and age groups. Reporting patterns in adults can differ from children, so this page's VAERS and international database breakdowns should be read with the reporting population in mind. Check the current CDC/ACIP adult schedule and the product's prescribing information for adult dosing.
10. Key References
IOM. Adverse Effects of Vaccines: Evidence and Causality. National Academies Press; 2012.
Klein NP, et al. Measles-mumps-rubella-varicella combination vaccine and the risk of febrile seizures. Pediatrics. 2010;126(1):e1–e8.