How does FDA evaluate vaccines to make sure they are safe?
FDA’s Center for Biologics Evaluation and Research is responsible for regulating vaccines in the U.S. Before new vaccines are licensed, they are tested extensively for safety in the laboratory, in animals, and in successive stages of human clinical trials called phases. When a new vaccine is first tested in humans, a sponsor (a vaccine manufacturer, academic investigator or other individual or organization) must first submit an Investigational New Drug Application to FDA. If data at any stage of clinical development raise significant concerns regarding the safety of the product, FDA may request additional information or may halt ongoing or planned studies. Phase 1 studies typically enroll less than 20 participants and are designed to look for very common adverse events. Phase 2 studies may include up to several hundred individuals and are designed to look at the overall safety profile of the vaccine for local reactions such as redness and swelling at the injection site as well as gener
