1. Basic Information

Respiratory syncytial virus (RSV) is a leading cause of bronchiolitis and pneumonia in infants and a significant cause of morbidity in older adults. U.S. prevention now includes three distinct product classes — not interchangeable:

Product	Type	Who	Manufacturer
Arexvy	Adjuvanted recombinant RSV vaccine (GSK)	Adults ≥60; pregnancy indication (maternal immunization)	GSK
Abrysvo	Bivalent recombinant RSV prefusion F vaccine (Pfizer)	Adults ≥60; maternal immunization (32–36 wks)	Pfizer
Beyfortus (nirsevimab)	Long-acting RSV monoclonal antibody — not a vaccine	Infants & toddlers (seasonal)	AstraZeneca / Sanofi

Source: FDA prescribing information; CDC RSV pages (2024–2026). Beyfortus reports in VAERS may appear under RSV product labels.

Ingredients (Package Insert)

Structured composition for 2 branded products 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.

Recombinant protein Intramuscular (IM) Adjuvant: AS01E No preservative (typical single-dose) Liposome Polysorbate 80

Arexvy GlaxoSmithKline Biologicals · Recombinant protein

Delivery

Route: Intramuscular (IM)

Form: Lyophilized powder (reconstitute)

Dose volume: 0.5 mL

Presentation: antigen vial + AS01E adjuvant suspension

Encapsulation / delivery vehicle

Liposome — AS01E is a liposomal adjuvant system (half-dose AS01 relative to AS01B).

Component	Role	Amount
DOPC	liposomal phospholipid	0.5 mg
Cholesterol	cholesterol	0.125 mg

Antigens

Antigen	Type	Amount / dose
Recombinant RSV prefusion F glycoprotein (RSVPreF3)	Recombinant protein	120 mcg

Adjuvants

AS01E — MPL 25 mcg + QS-21 25 mcg
- MPL — 25 mcg
- QS-21 — 25 mcg

Preservatives

None — Single-dose presentation; label states no preservative.

Excipients & residuals

Ingredient	Category	Amount	Role
Trehalose	Stabilizer	14.7 mg	stabilizer
Sodium chloride	Buffer	4.4 mg	tonicity
Potassium dihydrogen phosphate	Buffer	0.83 mg	buffer
Dipotassium phosphate	Buffer	0.26 mg	buffer
Polysorbate 80	Surfactant	0.18 mg	surfactant
Disodium phosphate anhydrous	Buffer	0.15 mg	buffer

Source: FDA package insert · Verified 2026-07-09

Abrysvo Pfizer Inc. · Recombinant protein

Delivery

Route: Intramuscular (IM)

Form: Lyophilized powder (reconstitute)

Dose volume: 0.5 mL

Presentation: single-dose vial + sterile water diluent / prefilled presentations per labeling

Encapsulation / delivery vehicle

None (no nanoparticle/VLP encapsulation system)

Antigens

Antigen	Type	Amount / dose
RSV prefusion F (bivalent: subgroup A and B) System: CHO cells	Recombinant protein	60 mcg each antigen (120 mcg total)

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.

Excipients & residuals

Ingredient	Category	Amount	Role
Tromethamine / tromethamine hydrochloride	Buffer	label quantity	buffer
Sucrose	Stabilizer	label quantity	stabilizer
Mannitol	Stabilizer	label quantity	stabilizer
Polysorbate 80	Surfactant	label quantity	surfactant
Sodium chloride	Buffer	label quantity	tonicity

Unadjuvanted protein subunit RSV vaccine (contrast Arexvy AS01E).

Source: FDA package insert · Verified 2026-07-09

ⓘ How to read this section

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.

Condition	Time window	Causality	Potential mechanism(s)
Anaphylaxis	0–1 days	Very likely / Probable Evidence: High	IgE-mediated hypersensitivity (anaphylaxis) (primary · hypersensitivity) 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.
Local/systemic reactogenicity	0–3 days	Very likely / Probable Evidence: High	Adjuvant-driven local and systemic reactogenicity (primary · innate_inflammation) Aluminum or other adjuvants (e.g., AS01B) amplify innate immune signaling, producing injection-site inflammation and transient systemic symptoms (fever, myalgia, fatigue).
Guillain-Barré Syndrome	0–42 days	Possible Evidence: Low	Molecular mimicry → Guillain-Barré syndrome (primary · molecular_mimicry) Vaccine- or infection-triggered immune responses cross-react with peripheral-nerve gangliosides or myelin components, producing demyelinating or axonal polyneuropathy. Temporal association — mechanism unknown (alternative · unknown) Reports show temporal clustering after vaccination but a specific pathogenic pathway is not established; alternative (coincidental) explanations remain plausible.
SIRVA	0–2 days	Very likely / Probable Evidence: High	SIRVA — incorrect injection into shoulder structures (primary · procedural) Needle placement into the subdeltoid/subacromial bursa or joint rather than deltoid muscle causes prolonged local inflammation and restricted range of motion (procedural, not antigen-specific).

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)

This vaccine is not listed in ICAN’s childhood-schedule No Placebo Table (which covers CDC routine pediatric injectable products). Pre-licensure trial comparators for travel, adult, or specialty vaccines should be taken from FDA review documents and product labels in the sections below.

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.

Product	Pivotal evidence	Common reactogenicity (trials)
Arexvy (AReSVi-006)	~82–89% efficacy vs. RSV-LRTD in adults ≥60 over one season	Injection-site pain, fatigue, myalgia, headache, arthralgia
Abrysvo (MATISSE maternal)	~82% efficacy vs. severe RSV disease in infants through 90 days when given in pregnancy	Maternal: injection-site pain, headache, myalgia; infant outcomes monitored in trials
Beyfortus (HARMONIE / MELODY)	~74–80% reduction in medically attended RSV LRTI in infants	Rash, injection-site reactions (mAb, not live virus)

Trial efficacy is against RSV disease endpoints — distinct from VAERS adverse-event report counts post-licensure.

3. Post-Licensure Safety Data

RSV preventives licensed in 2023–2024; post-marketing databases are still accumulating. Guillain-Barré syndrome signal monitoring was highlighted in FDA communications for older-adult RSV vaccines — see primary FDA reviews for context.

⚠ Critical Caveat

VAERS reports are unverified temporal associations. High report volume for new products partly reflects stimulated reporting and large rollout scale.

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 VigiAccess (WHO), Lareb (Netherlands), and DAEN (Australia) via SurVigilance. JADER: public CSV pmdacasereport202606. EudraVigilance: local EudraVigilance/ DAP exports. SurVigilance panels show MedDRA PT mention totals (not individual-case counts). Category assignment uses keyword matching — approximate, not official SOC coding. JADER reference (PDF)

VAERS (United States)

No VAERS category summary is mapped for this vaccine page.

Canada Vigilance (Canada)

No matching vaccine reports in the current Canada Vigilance extract.

JADER (PMDA, Japan)

No matching vaccine reports in the current JADER public extract.

EudraVigilance (EU)

No matching vaccine cases in the current EudraVigilance DAP export.

SurVigilance: VigiAccess, Lareb & DAEN

VigiAccess (WHO)

No VigiAccess data for this vaccine — run survigilance_pipeline.py.

Lareb (Netherlands)

No Lareb data for this vaccine — run survigilance_pipeline.py.

DAEN (Australia)

DAEN category breakdown not yet available for this vaccine.

Pipeline note: RSV products (Arexvy, Abrysvo, Beyfortus) are not yet mapped in VAERS category charts or Canada Vigilance extracts on this site — lot-level VAERS data below is the primary database view. Category assignment uses keyword matching on reported reaction terms — approximate and exploratory. Neither database establishes causality.

Active Pharmacovigilance (Defined-Population Surveillance)

Curated findings for RSV vaccines (Arexvy / Abrysvo) 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) / v-safe

Outcome: Pre-specified outcomes including Guillain-Barré syndrome and other serious events

Tier 2 ◐ Signal under investigation

RSV vaccines entered intensive post-licensure active monitoring in 2023–2024. Early pharmacovigilance attention has included evaluation of GBS and other rare outcomes after some products; status remains under active evaluation as seasons accumulate data. This is an expected phase for new vaccines, not a confirmed risk conclusion.

Population

Older adults and other recommended groups receiving RSV vaccine

Risk interval

Protocol-specific post-dose windows

Comparison

Control intervals / expected rates

Evaluation period

2023–ongoing (first U.S. seasons after licensure)

Method

Post-licensure active monitoring (RCA and survey systems as applicable)

Related passive AE category on this page: Neurological (see multi-system charts above — not additive with active rates).

Sources: CDC VSD · CDC RSV vaccination clinical guidance (safety context updates)

Record last reviewed: 2026-07-10

AusVaxSafety (Australia)

Outcome: Short-term solicited AEFI

Tier 1 ○ No signal detected

Where AusVaxSafety publishes RSV vaccine pages, short-term active survey results are used for early signal detection. Consult the live AusVaxSafety RSV pages for the latest respondent-based rates.

Population

Australian RSV vaccine recipients in AusVaxSafety

Risk interval

Early post-vaccination survey windows

Comparison

System thresholds

Evaluation period

2024–ongoing as products roll out

Method

Active survey surveillance for RSV vaccines where enrolled

Sources: AusVaxSafety safety data

Record last reviewed: 2026-07-10

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.

Compare AE patterns across all vaccines →

VAERS Lot-Level Reports

2,808 VAERS reports with usable lot data (U.S.). Signal flags are hypothesis-generating only — not proof of an unsafe lot. Full dashboard →

4. Disease Prevention Context

RSV causes an estimated 58,000–80,000 hospitalizations and 100–300 deaths annually among U.S. children <5 years (prevention era), and substantial burden in adults ≥65. Seasonal immunization and infant mAb programs aim to reduce LRTI hospitalization — effectiveness in real-world settings is tracked separately from pharmacovigilance report counts.

RSV Vaccine Side Effects (Arexvy, Abrysvo & Beyfortus — Adverse Event Database Reports)

1. Basic Information

Ingredients (Package Insert)

Antigens

Adjuvants

Preservatives

Excipients & residuals

Antigens

Adjuvants

Preservatives

Excipients & residuals

Causality assessment & potential mechanisms

2. Pre-Licensure Clinical Trial Data

Licensure trial design (ICAN / OpenVAERS)

3. Post-Licensure Safety Data

Passive Surveillance: AE Type Breakdown (Multi-System)

VAERS (United States)

Canada Vigilance (Canada)

JADER (PMDA, Japan)

EudraVigilance (EU)

SurVigilance: VigiAccess, Lareb & DAEN

VigiAccess (WHO)

Lareb (Netherlands)

DAEN (Australia)

Active Pharmacovigilance (Defined-Population Surveillance)

CDC Vaccine Safety Datalink (VSD) / v-safe

AusVaxSafety (Australia)

VAERS Lot-Level Reports

4. Disease Prevention Context

Part of the Open Source Medicine Foundation Network