As of Jan. 29, 501 deaths — a subset of 11,249 total adverse events — had been reported to the Centers for Disease Control and Prevention's (CDC) Vaccine Adverse Event Reporting System (VAERS) following COVID-19 vaccinations. The numbers reflect reports filed between Dec. 14, 2020, and Jan. 29, 2021.

VAERS is the primary mechanism for reporting adverse vaccine reactions in the U.S. Reports submitted to VAERS require further investigation before confirmation can be made that an adverse event was linked to a vaccine.

As of Jan. 29, about 35 million people in the U.S. had received one or both doses of a COVID vaccine. So far, only the Pfizer and Moderna vaccines have been granted Emergency Use Authorization in the U.S. by the U.S. Food and Drug Administration (FDA). By the FDA's own definition, the vaccines are still considered experimental until fully licensed.