In 1986, the National Childhood Vaccine Injury Act was enacted by Congress. The Department of Health and Human Services (HHS) established the Vaccine Adverse Event Reporting System (VAERS), co-administered by the U.S. Food and Drug Administration (FDA) and Centers for Disease Control and Prevention (CDC), to accept all reports of suspected adverse events, in all age groups, after the administration of any U.S.-licensed vaccine.

The Act required healthcare providers and vaccine manufacturers to report to the Department of Health and Human Services specific adverse events following the administration of measles, mumps, rubella, polio, pertussis, diphtheria, and tetanus vaccine and any combinations thereof.

FDA and CDC physicians continuously screen and analyze VAERS data for possible safety concerns related to the COVID-19 vaccines. For signals identified in VAERS, physicians from FDA and CDC screen individual reports, inclusive of comprehensive medical record review. Most reports do not represent adverse events caused by the vaccine and instead represent a pre-existing condition that preceded vaccination or an underlying medical condition that precipitated the event.