“VAERS is an early warning system used to monitor adverse events that happen after vaccination. VAERS is the frontline system of a comprehensive vaccine safety monitoring program in the United States. It is one of several systemspdf icon CDC and the U.S. Food and Drug Administration (FDA) use to help ensure vaccines used in the United States, including COVID-19 vaccines, are closely monitored for safety.”
Source: CDC Website
This graph is statistical analysis of the data collected by VAERS. It is estimated that VAERS collects only 1%-40% of adverse events, which you can adjust for on the right.