AbstractBackgroundOlder adults are vulnerable to both severe COVID-19 and RSV illness. Coadministration of RSV and COVID-19 vaccines could reduce healthcare visits for this population and potentially improve vaccine uptake. This study evaluated safety, tolerability, and immunogenicity of RSV and COVID-19 vaccines given together with or without seasonal quadrivalent influenza vaccine (QIV) as part of a larger clinical study looking at combination vaccines.MethodsThis phase 1/2 randomized study (NCT05886777) included healthy ≥ 65-year-olds who had received ≥ 3 previous mRNA COVID-19 vaccine doses (the most recent a bivalent vaccine given ≥ 150 days before study vaccine). In this study part, participants received coadministered RSVpreF and bivalent BA.4/BA.5-adapted BNT162b2 vaccine (RSVpreF/BNT162b2) with QIV or placebo; RSVpreF; BNT162b2; or QIV. Immunogenicity objectives included demonstration of noninferiority of neutralizing antibody titers elicited by RSVpreF/BNT162b2 compared to either vaccine administered alone, and by RSVpreF/BNT162b2 coadministered with QIV compared to RSVpreF, BNT162b2, and QIV alone (Figure 1).ResultsOf 766 participants in this analysis (149–158 per group), 46% were male, 89% White, 9% Hispanic/Latino. Median age was 71 (range 65–90) years. Based on the prespecified 2-fold margin, immune response noninferiority was demonstrated for RSVpreF/BNT162b2 for 2 RSV antigens and 2 SARS-CoV-2 strains versus RSVpreF or BNT162b2 alone (Figure 2). Noninferiority was also demonstrated for all 8 antigens (2 RSV; 2 SARS-CoV-2; 4 influenza) for immune responses elicited by RSVpreF/BNT162b2 administered with QIV versus those with RSVpreF, BNT162b2, or QIV alone (Figure 3). RSVpreF/BNT162b2 was well tolerated with mostly mild/moderate reactogenicity with rates generally similar across groups (Figure 4). Adverse events (AEs) were infrequent, mostly mild/moderate, and occurred at similar frequencies across groups. No AEs led to study withdrawal, and no serious AEs were considered vaccine related.ConclusionIn ≥ 65-year-olds, RSVpreF/BNT162b2 was safe and well tolerated, including when coadministered with QIV. The data support that RSVpreF and BNT162b2 can be administered concomitantly, which may support improved uptake of both vaccines.Funding: Pfizer Inc.DisclosuresJoel Neutel, MD, Pfizer Inc: Employee Rahsan Erdem, MD, Pfizer Inc: Employee|Pfizer Inc: Stocks/Bonds (Private Company) Qin Jiang, PhD, Pfizer: Salary|Pfizer: Stocks/Bonds (Public Company) Ryan Newton, BSC/MBA, Pfizer Inc: Employee|Pfizer Inc: Stocks/Bonds (Private Company) Emily A. Gomme, Ph.D., Pfizer Inc: Employee|Pfizer Inc: Stocks/Bonds (Private Company) Federico Mensa, MD, BioNTech: Employee|BioNTech: Stocks/Bonds (Public Company) Ozlem Tureci, MD, BioNTech: Employee|BioNTech: Stocks/Bonds (Public Company) Ugur Sahin, MD, BioNTech: Employee|BioNTech: Stocks/Bonds (Public Company) Kena A. Swanson, Ph.D., Pfizer: Employee of Pfizer|Pfizer: Stocks/Bonds (Public Company) Iona Munjal, MD, Pfizer: Salaried employee|Pfizer: Stocks/Bonds (Public Company) David Cooper, PhD, Pfizer, Inc.: Employee|Pfizer, Inc.: Stocks/Bonds (Public Company) Kenneth Koury, PhD, Pfizer Inc: Employee|Pfizer Inc: Stocks/Bonds (Public Company) Annaliesa S. Anderson, PhD, Pfizer, Inc.: Employee|Pfizer, Inc.: Stocks/Bonds (Public Company) Alejandra C. Gurtman, M.D., Pfizer, Inc.: Employee|Pfizer, Inc.: Stocks/Bonds (Public Company) Nicholas Kitchin, MD, Pfizer Inc: Employee|Pfizer Inc: Stocks/Bonds (Public Company)