The U.S. Food and Drug Administration (FDA) granted Emergency Use Authorization (EUA) for the COVID-19 vaccines from Pfizer-BioNTech (December 11, 2020) and Moderna (December 18, 2020). At the January 27, 2021 meeting of the Center for Disease Control and Prevention (CDC) Advisory Committee on Immunization Practices (ACIP), a member of CDC’s vaccine safety team provided a safety update on both vaccines based on information reported to CDC by both health care providers and people who had received one or two doses of the vaccines as of January 14, 2021. By this date, 23.4 million vaccine doses had been administered in the U.S. Overall, the safety profiles of COVID-19 vaccines are reassuring and consistent with safety data observed from the pre-authorization clinical trials.
CDC and the FDA use several mechanisms and databases for the ongoing collection and evaluation of COVID-19 vaccine safety data as these new vaccines are administered across the U.S. A comprehensive, COVID-10 vaccine safety monitoring system was put in place by CDC to conduct post-marketing surveillance of COVID-19 vaccines following the issuance of EUAs. The presentation at the ACIP meeting on January 27 reported on vaccine safety data from several monitoring programs including v-safe, the Vaccine Adverse Event Reporting System (VAERS), and the Vaccine Safety Datalink (VSD) platform as noted below. In addition, Pfizer-BioNTech and Moderna must submit periodic vaccine safety reports to the FDA and report serious adverse events to VAERS.
The smartphone-based v-safe is an “after vaccination health checker” where people who have received a COVID-19 vaccine can quickly tell CDC about any side effects they experienced. Based on information reported to v-safe as of January 14, side effects (such as headache, fatigue and muscle soreness) reported have been similar to those reported in the Phase 3 clinical trials.
Another mechanism to capture side effect information for vaccines is the Vaccine Adverse Event Reporting System (VAERS) which is co-managed by CDC and the FDA. VAERS accepts reports from everyone regardless of the whether the vaccine caused the side effect or the level of clinical seriousness of the event. However, VAERS can rapidly detect safety “signals” and rare adverse events that warrant further investigation. The most reported adverse events for either the Pfizer-BioNTech or Moderna vaccines as of January 18 included headache, fatigue, fever, dizziness, chills, and pain, like the most frequent side effects reported in the v-safe platform. Concerning the rare occurrence of anaphylaxis following vaccine administration, the available data indicate that 5.0 cases of anaphylaxis have occurred for every one million doses of the Pfizer-BioNTech vaccine administered and 2.8 cases have occurred for every one million doses of the Moderna vaccine administered.
CDC also utilizes the Vaccine Safety Datalink (VSD), a collaborative project with nine health care organizations across the country to monitor possible adverse events when new vaccines are licensed (or authorized for emergency use such as for the current COVID-19 vaccines). Notably, CDC can assess if the rate of adverse events among vaccinated people is higher than among a comparison unvaccinated group; a higher rate of specific adverse events in vaccinated people may represent a “safety signal” that needs further attention. As of January 16, 2021, no such safety signals were detected among people vaccinated with either the Pfizer-BioNTech or Moderna vaccines as compared to the unvaccinated population. While the Phase 3 studies of both vaccines noted a few more cases of Bell’s Palsy occurring in the vaccinated groups vs. the placebo arms, Bell’s Palsy did not represent a safety signal in the VSD analysis. There were no reported cases of anaphylaxis in the VSD analysis among those vaccinated with either vaccine.