Tens of thousands of people volunteered for what are called clinical trials to find out whether a vaccine is safe and effective at protecting people from COVID-19. These trials include people of racially and ethnically diverse backgrounds. The results of the trials are reviewed by independent experts, companies that are making the vaccine, and a federal government agency called the Food and Drug Administration (FDA).
Trials for the COVID-19 vaccine began earlier this year, and the Pfizer-BioNTech and Moderna vaccines that have received Emergency Use Authorizations from the Food and Drug Administration were found to be 95 and 94 percent effective, respectively, which is terrific. Vaccine safety gets assessed based on the experience of volunteers who received the vaccine during the trials. Thousands of volunteers are followed closely for at least two months to monitor their health before the vaccine can be authorized for use. Any negative reactions to a vaccine would most likely happen within that period. The volunteers are also observed long-term to monitor for any other problems.
Updated 19 December 2020