Abstract
BACKGROUND: Seasonal influenza epidemics are managed through vaccination each winter in the European Union, to prevent infections, complications, and deaths. As circulating virus strains vary unpredictably, vaccines are reformulated annually, and their safety monitored rapidly and continuously at the start of each season, following European Medicines Agency guidelines.Seasonal influenza epidemics are managed through vaccination each winter in the European Union, to prevent infections, complications, and deaths. As circulating virus strains vary unpredictably, vaccines are reformulated annually, and their safety monitored rapidly and continuously at the start of each season, following European Medicines Agency guidelines. METHODS: This enhanced safety surveillance study assessed pre-specified and other adverse events (AEs) occurring within 7 days of GSK's inactivated quadrivalent seasonal influenza vaccine (IIV4) in children and adults in Spain and Germany. As the study was conducted during the COVID-19 pandemic (2021/2022 season), data were collected electronically, using a web portal or call center. RESULTS: Safety was assessed in 737 participants (median age 49 and 9 years in Germany and Spain, respectively, 19.3% with a chronic medical condition). After Dose 1 and Dose 2, respectively, 332 (45.1%) and 5 (26.3%) participants reported at least one AE, primarily pre-specified AEs. The most common AEs after Dose 1 (adults and children) were injection site pain, swelling or erythema, headache, and fatigue. After Dose 2 (in children), the most common AEs were injection site pain, rhinorrhea, fatigue, and decreased appetite. No new or unexpected safety issues were identified. CONCLUSION: This study supports and confirms the safety profile of GSK's IIV4 in all age groups with a vaccine indication. The new electronic safety reporting method (with response rates of 75.4% following Dose 1 and 100% following Dose 2) provides an alternative for future studies to reduce the burden on sites or in case site visits are not feasible.