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.
What VAERS is
The Vaccine Adverse Event Reporting System (VAERS) is the U.S. passive reporting system co-managed by CDC and FDA. Anyone can file a report; most are not verified as vaccine-caused events.
Three ways to use VAERS data on this site
- Category overview — symptom-type breakdowns across vaccines
- Lot / batch lookup — enter a vaccine lot number, see VAERS reports for that batch (signature tool)
- Per-vaccine pages — e.g. Tdap, shingles
Official VAERS access
Raw downloads and WONDER queries: vaers.hhs.gov/data.html. Expect steep learning curve — that usability gap is why this navigator exists.
Related: Vaccine side effects index · Lot / batch lookup