Vaccine Adverse Event Reporting System

The Vaccine Adverse Event Reporting System (VAERS) is a United States program for vaccine safety, co-managed by the U.S. Centers for Disease Control and Prevention (CDC) and the Food and Drug Administration (FDA). VAERS is a postmarketing surveillance program, collecting information about adverse events (possible harmful side effects) that occur after administration of vaccines to ascertain whether the risk–benefit ratio is high enough to justify continued use of any particular vaccine.

Source: Wikipedia — Vaccine Adverse Event Reporting System (CC BY-SA 4.0)