219. Robust and Consistent Immune Response of the Adjuvanted Respiratory Syncytial Virus (RSV) Prefusion F Protein Vaccine (RSVPreF3 OA) Across Different Age Ranges and Frailty Status in Older Adults

Abstract Background In a phase 3 study, the approved RSVPreF3 OA vaccine, administered as a single dose in adults aged ≥ 60 years, has demonstrated high efficacy against RSV disease and was well tolerated with a favorable safety profile. Here we present immunogenicity results in older adults of different age and frailty status from the same study. Methods This phase 3, placebo-controlled, observer-blind, multi-country study (NCT04886596) enrolled adults aged ≥ 60 years who were randomized (1:1) to receive a dose of RSVPreF3 OA or placebo, before the RSV season. Blood samples were collected at pre-vaccination (day 1) and 1 month post-vaccination (day 31). Humoral immune responses were assessed in a subset of participants, and outcomes included RSV-A and RSV-B neutralization titers by age category and frailty status. Results Of the 24,966 participants who received RSVPreF3 OA or placebo at day 1, 1,702 were included in the per-protocol set for immunogenicity. Demographic characteristics in the immunogenicity subset were well balanced between groups (Table 1). The mean age was 70.3 (± 6.8) years. At day 1, all tested participants had detectable RSV-A and RSV-B neutralization titers due to previous exposure to RSV. At day 31, 1 month post-vaccination, neutralization titers were between 9.4–11.3-fold (RSV-A) and between 8.0–9.0-fold (RSV-B) higher than pre-vaccination levels across the different age categories (Figure 1). In pre-frail and frail adults, neutralization titers increased 10.0- and 13.7-fold (RSV-A), and 8.8- and 9.2-fold (RSV-B) between day 1 and 1 month post-vaccination (Figure 1). Conclusion For both RSV subtypes, RSVPreF3 OA induced a large increase in neutralization titers across the different age categories, including a robust immune response even in adults aged ≥80 years, known to have immunosenescence. A robust immune response was also observed in pre-frail and frail adults, however the results for frail adults should be considered with caution as the number of frail adults in the study was low. Funding: GSK Disclosures Isabel Leroux-Roels, PhD MD, Curevac: Grant/Research Support|GSK: Grant/Research Support|Icosavax: Grant/Research Support|Janseen Vaccines: Advisor/Consultant|Janseen Vaccines: Board Member|Janseen Vaccines: Grant/Research Support|Moderna: Grant/Research Support|MSD: Advisor/Consultant|MSD: Grant/Research Support|OSE Immunotherapeutics: Grant/Research Support|Osivax: Grant/Research Support Robert G. Feldman, MD, GSK: Payment to attend congress and speaking events, travel expenses for these events Raffaele Antonelli-Incalzi, MD, GSK: Grant/Research Support Alberto Papi, MD, Agenzia Italiana del farmaco (AIFA): Grant/Research Support|AstraZeneca: Advisor/Consultant|AstraZeneca: Board Member|AstraZeneca: Grant/Research Support|AstraZeneca: Honoraria|Avillion: Advisor/Consultant|Avillion: Board Member|Avillion: Honoraria|CHIESI: Advisor/Consultant|CHIESI: Board Member|CHIESI: Grant/Research Support|CHIESI: Honoraria|Edmond Pharma: Advisor/Consultant|Edmond Pharma: Honoraria|Elpen Pharmaceutica: Advisor/Consultant|Elpen Pharmaceutica: Board Member|Elpen Pharmaceutica: Honoraria|GSK: Advisor/Consultant|GSK: Board Member|GSK: Grant/Research Support|GSK: Honoraria|IQVIA: Board Member|IQVIA: Honoraria|Menarini: Honoraria|Mundipharma: Honoraria|Novartis: Advisor/Consultant|Novartis: Board Member|Novartis: Honoraria|Sanofi: Advisor/Consultant|Sanofi: Board Member|Sanofi: Grant/Research Support|Sanofi: Honoraria|Zambon: Advisor/Consultant|Zambon: Honoraria Michael G. Ison, MD MS, Adagio: Advisor/Consultant|Adamis: Advisor/Consultant|Adamis: Board Member|ADMA Biologics: Advisor/Consultant|AlloVir: Advisor/Consultant|AlloVir: Board Member|Cidara: Advisor/Consultant|CSL Behring: Board Member|Genentech: Advisor/Consultant|GSK: Grant/Research Support|ISIRV AVG: Chair|Janssen: Advisor/Consultant|Janssen: Board Member|Merck: Board Member|NIH: Board Member|Roche: Advisor/Consultant|Sequiris: Board Member|Shinogi: Advisor/Consultant|Takeda: Advisor/Consultant|Takeda: Board Member|Talaris: Advisor/Consultant|Talaris: Board Member|Transplant Infectious Disease: Editor-in-Chief|UpToDate: Royalties Marie-Pierre David, Master in Statistics, GSK: As GSK employee, I’m part of a patent application|GSK: Salary as GSK employee with stock options|GSK: Stocks/Bonds (Public Company) Carline Vanden Abeele, MS, GSK: Salary as GSK employee with stock options|GSK: Stocks/Bonds (Public Company) Magali de Heusch, PhD, GSK: Salary as GSK employee with stock options|GSK: Stocks/Bonds (Public Company) Nathalie De Schrevel, PhD, GSK: Magali De Heusch|GSK: Stocks/Bonds (Public Company) Catherine Gerard, PhD, GSK: Salary as GSK employee with stock options|GSK: Stocks/Bonds (Public Company) Aurélie Olivier, PhD, GSK: As GSK employee, I’m part of a patent application|GSK: employee|GSK: Stocks/Bonds (Public Company) Marie Van Der Wielen, MD, GSK: As GSK employee, I’m part of a patent application|GSK: Salary as GSK employee with stock options|GSK: Stocks/Bonds (Public Company) Veronica Hulstrøm, MD, PhD, GSK: Salary as GSK employee with stock options|GSK: Stocks/Bonds (Public Company)