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Preservatives are compounds that kill or prevent the growth of microorganisms, such as bacteria or fungi. What are preservatives and why are they added to vaccines? One such system is the Vaccine Safety Datalink, administered by the CDC. In addition, controlled epidemiological studies may be conducted using pre-established large-linked databases, which have improved ability to evaluate whether rare adverse events are caused by vaccination. As part of a post-licensure commitment, FDA often asks the manufacturer to conduct additional clinical studies (sometimes called phase 4 studies), to further evaluate safety, and to provide this information to FDA in a timely manner. VAERS is useful, however, for raising 'red-flags' and subsequently generating hypotheses that can be tested further in controlled clinical trials or epidemiological studies. As a spontaneous reporting system, VAERS has several limitations including under-reporting, incompleteness of reports, lack of consistent diagnostic criteria, and the inability in most cases to establish a cause and effect relationship. The Vaccine Adverse Event Reporting System, co-administered by FDA and CDC, is a national passive surveillance system for the collection of all reports of adverse events following vaccination. The safety of new vaccines continues to be monitored following licensure in several ways. Vaccine approval also requires the provision of adequate information (labeling) to health care providers and the public on the vaccine's proper use, including its potential benefits and risks, and its indications and contraindications. The advisory committee provides advice to FDA on approval or disapproval.

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If product development is successful, the completion of all three phases of clinical development can be followed by submission of a Biologics License Application (BLA).įollowing FDA's review of a license application for a new indication, the sponsor and FDA usually present their findings to an expert advisory committee in an open public meeting for comment and advice. In addition, FDA carefully reviews information on the manufacturing process of new vaccines, and testing is performed on individual lots for safety and potency. For vaccines given concomitantly with other vaccines under the routine immunization schedules, the safety of new vaccines typically is studied with concurrent administration of these other vaccines. Phase 3 studies are usually of sufficient size to detect less common adverse events, such as those occurring at rates of 1 in 100 to 1 in 1000. For phase 3 studies, the sample size is often determined by the number required to establish efficacy of the new vaccine, which may be in the thousands or tens of thousands of subjects. 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 general side effects that may occur with some vaccines such as fever. Phase 1 studies typically enroll less than 20 participants and are designed to look for very common adverse events. 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. 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. 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. How does FDA evaluate vaccines to make sure they are safe?įDA's Center for Biologics Evaluation and Research is responsible for regulating vaccines in the U.S. Questions about Thimerosal in Vaccine regarding Infants, Children, and Pregnant Women.