Brand-Specific Enhanced Safety Surveillance Study of GSK's Quadrivalent Seasonal Influenza Vaccine, Conducted During the COVID-19 Pandemic, in Belgium, Germany and Spain, for the 2020/21 Season

Abstract

Introduction: Seasonal influenza poses a major public health burden worldwide. Influenza vaccines, updated yearly to match circulating strains based on World Health Organization (WHO) recommendations, are the cornerstone of prevention and require regular monitoring. The COVID-19 pandemic is expected to cause logistical, site access and medical staff constraints and could affect the safety profile of influenza vaccines.

Methods: Following European Medicines Agency guidance, an enhanced safety surveillance (ESS) study assessed the frequency and severity of predefined and other adverse events (AEs) occurring within 7 days of receiving GSK's inactivated quadrivalent seasonal influenza vaccine (IIV4), in Belgium, Germany and Spain in 2020/21, using adverse drug reaction (ADR) cards.

Results: During the 2020/21 influenza season, 1054 participants vaccinated with GSK's IIV4 were enrolled (all adults in Belgium and Germany, 30% adults/70% children in Spain); 96 eligible children received a second dose. Overall, 1042 participants completed the study. After doses 1 and 2, 98.9% and 100% of participants, respectively, returned their completed ADR card. After doses 1 and 2, 37.8% (398/1054) and 13.5% (13/96) of participants, respectively, reported at least one AE. The most frequently reported categories of AEs were "general disorders and administration site conditions" (e.g. injection site pain) and "nervous system disorders" (e.g. headache). There were no deaths or serious AEs deemed related to GSK's IIV4.

Conclusion: This ESS study assessed AEs in near real time. The COVID-19 pandemic did not alter the safety profile of GSK's IIV4. No safety signals were detected during the study, which confirms the excellent safety profile of GSK's IIV4.

Keywords: AlphaRix Tetra; Fluarix Tetra; Infectious disease; Influenza; Influsplit Tetra; Post-marketing surveillance; Vaccination; Vaccine Safety; Vaccine monitoring.

Fig. 1

Attrition diagram. *Of 321 enrolled children (aged 6 months to 17 years), 96 were eligible for dose 2, i.e. receiving the seasonal influenza vaccine for the first time and less than 9 years of age at inclusion. IIV4, inactivated quadrivalent seasonal influenza vaccine; N, total number of participants; n, number of participants in a specific category

Fig. 2

Number of enrolled participants (cumulative, by ISO week) with proportion reporting at least one AE after dose 1 or dose 2 (safety set). AE, adverse event; ISO, International Organization for Standardization. Cumulative number of enrolled participants by week and by country, with the proportion reporting at least one AE. Participants in Germany and Belgium were adults and therefore received only one dose of GSK’s inactivated quadrivalent seasonal influenza vaccine, while some participants in Spain were children eligible for two doses. Participants were enrolled from ISO week 40, 2020 (28 September–4 October 2020) to ISO week 2, 2021 (11–17 January 2021)