ABSTRACT
The Food and Drug Administration (FDA) approves vaccines when their benefits outweigh the risks for their intended use. In this article we review the standard FDA approach to vaccine evaluation, which underpins its current approaches to assessment of vaccines to prevent coronavirus disease 2019 (COVID-19). The FDA has established pathways to accelerate vaccine availability before approval, such as Emergency Use Authorization, and to channel resources to high-priority products and allow more flexibility in the evidence required for approval, including accelerated approval based on surrogate markers of effectiveness. Among the thirty-five new vaccines approved in the US from 2006 through October 2020, about two-thirds of their pivotal trials used the surrogate outcome of immune system response, and only one-third evaluated actual disease incidence. Postapproval safety surveillance of new vaccines, and particularly vaccines receiving expedited approval, is crucial. This has generally been accomplished through such mechanisms as the Centers for Disease Control and Prevention (CDC) and FDA Vaccine Adverse Event Reporting System, the CDC Vaccine Safety Datalink, and the CDC Clinical Immunization Safety Assessment Project. Adverse events detected in this way may lead to changes in a vaccine's recommended use or withdrawal from the market. Regulatory oversight of new vaccines must balance speed with rigor to effectively address the pandemic.