No vaccine or medical product is 100% safe, but the safety of vaccines is ensured via rigorous testing in clinical trials prior to authorization or approval, followed by continued safety monitoring once the vaccine is rolled out to the public to detect potential rare side effects. In addition, the Food and Drug Administration inspects vaccine production facilities and reviews manufacturing protocols to make sure vaccine doses are of high-quality and free of contaminants.
One key vaccine safety surveillance program is the Vaccine Adverse Event Reporting System, or VAERS, which is an early warning system run by the Centers for Disease Control and Prevention and FDA. As its website explains, VAERS “is not designed to detect if a vaccine caused an adverse event, but it can identify unusual or unexpected patterns of reporting that might indicate possible safety problems requiring a closer look.”
Anyone can submit a report to VAERS for any health problem that occurs after an immunization. There is no screening or vetting of the report and no attempt to determine if the vaccine was responsible for the problem. The information is still valuable because it’s a way of being quickly alerted to a potential safety issue with a vaccine, which can then be followed-up by government scientists.
Another monitoring system is the CDC’s Vaccine Safety Datalink, which uses electronic health data from nine health care organizations in the U.S. to identify adverse events related to vaccination in near real time.
In the case of the COVID-19 vaccines, randomized controlled trials involving tens of thousands of people, which were reviewed by multiple groups of experts, revealed no serious safety issues and showed that the benefits outweigh the risks.
The CDC and FDA vaccine safety monitoring systems, which were expanded for the COVID-19 vaccines and also include a new smartphone-based reporting tool called v-safe, have subsequently identified only a few, very rare adverse events.
For more, see “How safe are the vaccines?”