Common questions about VAERS data, our methodology, and how to interpret vaccine adverse event reports.
The Vaccine Adverse Event Reporting System (VAERS) is a national early warning system co-managed by the CDC and FDA to detect possible safety problems in U.S.-licensed vaccines. It accepts reports of adverse events that occur after vaccination from healthcare providers, manufacturers, and the public.
No. VAERS reports describe events that happened after vaccination, but this temporal association does not prove causation. Many reported events may be coincidental, occurring at the same rate they would in an unvaccinated population. Reports may also contain incomplete or inaccurate information.
COVID-19 vaccines were administered to hundreds of millions of people in a short timeframe, during a period of intense public scrutiny and media attention. This led to dramatically higher reporting rates compared to other vaccines — a well-documented phenomenon called "stimulated reporting." More reports does not necessarily mean more risk.
Anyone can file a VAERS report — healthcare providers, vaccine manufacturers, patients, and family members. Healthcare providers are legally required to report certain serious adverse events. This openness is both a strength (broad signal detection) and a limitation (unverified reports).
We process the raw VAERS data files published quarterly by the CDC/FDA and present them in an accessible, searchable format. We add context, disclaimers, and analysis to help people understand what the numbers mean — and what they don't mean.
VAERS data is published quarterly by the CDC/FDA. We update our database shortly after each new data release. The current dataset includes reports through 2026.
Report volume is primarily driven by how many doses of a vaccine have been administered, public awareness, media attention, and mandatory reporting requirements. Higher report counts do not indicate higher risk. See our analysis on the denominator problem for more context.
VAERS provides report counts (numerators) but not the number of vaccine doses administered (denominators). Without knowing how many people received each vaccine, raw report counts cannot be used to calculate or compare risk rates. This is the single most important limitation of VAERS data.
Neither. We are a data transparency project. We present VAERS data as-is, with appropriate context and disclaimers. We don't make recommendations about vaccination. Our goal is informed transparency — helping people understand the data so they can have better conversations with their healthcare providers.
This website is for educational and informational purposes only. It is not medical advice. Always consult qualified healthcare professionals for medical decisions, including vaccination decisions.
We define serious outcomes as reports that mention death or hospitalization. The serious outcome rate is (deaths + hospitalizations) / total reports × 100. This is a rough measure of report severity, not a measure of vaccine risk.
VaccineWatch is part of TheDataProject.ai, a collection of data transparency tools. Our sister sites include OpenMedicaid, OpenFeds, OpenSpending, OpenMedicare, and OpenLobby — all focused on making government data accessible and understandable.
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