Lessons learned from COVID-19, H1N1, and routine vaccine pharmacovigilance in the United States: a path to a more robust vaccine safety program

Introduction: Vaccine pharmacovigilance is an essential component of vaccine safety programs. Vaccine pharmacovigilance refers to detecting uncommon adverse events following immunization (AEFI), determining whether they are due to the vaccine or are only a coincidence, and, for those AEFI considered related to vaccination, characterizing them further. When AEFI are due to vaccination, it is important to characterize the attributable risk and ascertain the biological mechanism causing the adverse reaction to inform efforts to prevent or mitigate the risk. A robust post-authorization safety system is necessary for vaccine decision-making, clinical recommendations, vaccine compensation, and vaccine communication and confidence. Areas Covered: This paper describes the key characteristics of vaccine pharmacovigilance programs, reviews US vaccine pharmacovigilance for routine vaccination programs, COVID-19, and H1N1, and makes recommendations for improving future vaccine safety systems. Expert Opinion: The key characteristics of vaccine pharmacovigilance programs include passive surveillance, active surveillance, clinical investigation and special studies, and causality assessment. Recent examples illustrate the strengths of US pharmacovigilance systems, including systems for passive and active surveillance, as well as areas for improvement, including study of pathogenesis, consistent funding, and leadership. We make recommendations that would, if implemented, further strengthen the vaccine safety system for future routine and pandemic immunizations.