COVID-19 Vaccine FAQs
Understanding How COVID-19 Vaccines Work
8 Things to Know about the U.S. COVID-19 Vaccination Program
Understanding mRNA COVID-19 Vaccines
Safety of COVID-19 Vaccines
The U.S. Food and Drug Administration (FDA) has granted Emergency Use Authorizations (EUA) for two COVID-19 vaccines which have been shown to be safe and effective as determined by data from the manufacturers and findings from large clinical trials. These data demonstrate that the known and potential benefits of this vaccine outweigh the known and potential harms of becoming infected with the coronavirus disease 2019 (COVID 19).
Clinical trials are being conducted to evaluate additional COVID-19 vaccines in many thousands of study participants. These trials will generate scientific data and other information that will be used by FDA to determine vaccine safety and effectiveness. Clinical trials on all COVID-19 vaccine candidates are being conducted according to the rigorous standards set forth by FDA in their June 2020 guidance document, Development and Licensure of Vaccines to Prevent COVID-19external icon. If FDA determines that a vaccine meets its safety and effectiveness standards, it can make these vaccines available for use in the United States by approval or through an EUA.
After FDA determines that a COVID-19 vaccine candidate is safe and effective, the Advisory Committee on Immunization Practices (ACIP), a committee comprising medical and public health experts, reviews available data before making vaccine recommendations to CDC. Learn more about how CDC is making COVID-19 vaccine recommendations.
Vaccine Safety Monitoring
After a vaccine is authorized or approved for use, many vaccine safety monitoring systems watch for adverse events (possible side effects). This continued monitoring can pick up on adverse events that may not have been seen in clinical trials. If an unexpected adverse event is seen, experts quickly study it further to assess whether it is a true safety concern. Experts then decide whether changes are needed in U.S. vaccine recommendations. This monitoring is critical to help ensure that the benefits continue to outweigh the risks for people who receive vaccines.
FDA’s June 2020 guidance document also includes important recommendations for ongoing safety evaluation after any COVID-19 vaccine is made available in the United States.
CDC has expanded safety surveillance through new systems and additional information sources, as well as by scaling up existing safety monitoring systems.