Even after a vaccine gains approval and is licensed, its safety is closely monitored by the FDA and the Centers for Disease Control and Prevention (CDC). This helps identify any possible risks of the vaccine. To help monitor vaccine safety, several reporting systems collect information about vaccine use: Clinical Immunization Safety Assessment Project (CISA) is a partnership between the CDC and seven research centers; it helps health care providers answer complex questions about vaccine safety and conducts clinical studies around vaccine safety
Post-Licensure Rapid Immunization Safety Monitoring (PRISM) is a network of health care organizations from across the U.S. that analyzes the health care data of more than 190 million people
Vaccine Adverse Event Reporting System (VAERS) collects reports of adverse side effects from health care providers, parents and patients, and then analyzes the information for safety concerns
Vaccine Safety Datalink (VSD) is a network of health care organizations from across the U.S. that analyzes the health care records of more than 24 million people
If a vaccine is found to have a serious risk or side effect, the recommendations for its use may change.