Postmarketing safety surveillance of high-dose quadrivalent influenza vaccine: Reports to the Vaccine Adverse Event Reporting System.

On November 4, 2019, the Food and Drug Administration approved high-dose quadrivalent influenza vaccine (Fluzone High-Dose Quadrivalent; QIV-HD) for active immunization for the prevention of influenza disease in individuals 65 years of age and older. A prelicensure randomized, active-controlled, modified double-blind trial did not reveal any major differences in adverse events following QIV-HD versus Fluzone High-Dose (trivalent). To improve our understanding of the safety profile of QIV-HD, we reviewed and summarized reports of adverse events after QIV-HD to the Vaccine Adverse Event Reporting System (VAERS). From July 30, 2020 through June 30, 2021, VAERS received 2,122 reports after QIV-HD. The vast majority (2,018; 95.1%) were non-serious and included events that had been observed in the prelicensure clinical trial, such as injection site reactions, fever, headache, and nausea. The most common serious events included Guillain-Barré syndrome, cellulitis or other local reactions, constitutional signs/symptoms (e.g., fever), and cardiovascular events. Our review did not reveal any new safety concerns. This information may enable policy makers, health officials, clinicians, and patients to make a more informed decision regarding vaccination strategies.