P-711. Persistence of Immunogenicity and Safety of the Respiratory Syncytial Virus Prefusion F Protein Vaccine (RSVPreF3 OA) Administered to Adults 50–59 Years of Age (YOA)
Authors: Ferguson Murdo , Schwarz Tino F , Núñez Sebastián A , García Juan Rodríguez , Mital Marek , Zala Carlos , Pek Bonavuth , Schmitt Bernhard , Toursarkissian Nicole , Mazarro Dolores Ochoa , Grosskopf Josef , Voors-Pette Christine , Mehta Hemalini , Hailemariam Hiwot Amare , Portaels Caroline , de Heusch Magali , Salaun Bruno , Damaso Silvia , David Marie-Pierre , Descamps Dominique , Hill Judith , Vandermeulen Corinne , Hulstrøm Veronica 
Published: January 2025

Abstract

Background
The immune response induced by RSVPreF3 OA in adults 50–59 YOA, including adults with chronic conditions that increase the risk for RSV disease, was non-inferior in terms of RSV-A/-B neutralization titers compared to that in older adults (≥ 60 YOA) at 1 month (M) post-vaccination.

Methods
This was a phase 3, observer-blind, placebo-controlled multi-country study (NCT05590403). Adults 50–59 YOA at increased risk (AIR) for RSV disease due to specific chronic conditions and not at increased risk for RSV disease (non-AIR) 50–59 YOA adults were randomized (2:1) to receive 1 dose of RSVPreF3 OA (AIR-RSV, non-AIR-RSV) or placebo (AIR-placebo, non-AIR-placebo). A control group of adults ≥ 60 YOA received RSVPreF3 OA (RSV-OA). We assessed the immune response at 1M and 6M post-vaccination. Humoral immunity (HI) and cell-mediated immunity (CMI) were assessed in terms of RSV-A/-B neutralization titers and RSVPreF3-specific CD4+ T-cell frequencies. Safety up to study end (12M post-vaccination) was also assessed.

Results
1533 participants received RSVPreF3 OA or placebo. In all RSV groups, RSV-A/-B neutralization titers (Figure 1) and RSVPreF3-specific CD4+ T-cell frequencies (Figure 2) increased substantially from pre-vaccination to 1M post-vaccination and remained above baseline levels at 6M (4.9–5.2-fold for RSV-A and 3.3–3.6-fold RSV-B neutralization titers). Within 6M post-vaccination, 3.9% (AIR-RSV), 0.8% (non-AIR-RSV), 2.1% (AIR-placebo, non-AIR-placebo) and 2.4% (RSV-OA) of participants reported serious adverse events (SAEs). Eight potential immune-mediated diseases (AIR-RSV: 4; AIR-placebo: 1; RSV-OA: 3) were reported within 6M post-vaccination. Of these, one case of cold type hemolytic anemia (RSV-OA, onset at day 53 post-vaccination, also SAE) was considered vaccine-related by the investigator. Five deaths (AIR-RSV: 4; AIR-placebo: 1), none considered vaccine-related, were reported up to study end (12M).

Conclusion
At 6M post-vaccination, HI and CMI remained above baseline both in RSVPreF3 OA-vaccinated adults 50–59 YOA with/without chronic conditions and in adults ≥60 YOA (RSV-OA). Up to 12M, the safety profile in adults 50–59 YOA was similar to the safety profile in those ≥ 60 YOA and was considered acceptable.
Funding: GSK

Disclosures
Murdo Ferguson, MD, GSK: Study related payments for training and the conduct of the study as a study site Tino F. Schwarz, Prof. Dr. MD, AstraZeneca: Honoraria|Bavarian Nordic: Advisor/Consultant|Bavarian Nordic: Honoraria|Biogen: Honoraria|Biontech: Advisor/Consultant|Biontech: Honoraria|CSL Vifor: Honoraria|CSL-Seqirus: Advisor/Consultant|CSL-Seqirus: Honoraria|Diasorin: Honoraria|GSK: Advisor/Consultant|GSK: Honoraria|Janssen-Cilag: Honoraria|Merck-Serono: Honoraria|Moderna: Advisor/Consultant|Moderna: Honoraria|MSD: Honoraria|Novavax: Advisor/Consultant|Novavax: Honoraria|Pfiser: Honoraria|Roche: Honoraria|Sanofi-Aventis: Honoraria|Synlab: Honoraria|Takeda: Advisor/Consultant|Takeda: Honoraria Sebastián A. Núñez, Dr., GSK: Support for attending meetings and/or travel Juan Rodríguez García, MD, GSK: Advisor/Consultant|GSK: Grant/Research Support|GSK: Honoraria|Pfizer: Honoraria|Pfizer: Support for attending meetings and/or travel|Sanofi: Honoraria|Sanofi: Support for attending meetings and/or travel Carlos Zala, MD, GSK: Grant/Research Support|GSK: Support for attending meetings and/or travel (EACS 2023) Josef Grosskopf, MD, GSK: Advisor/Consultant|GSK: Expert Testimony|GSK: Grant/Research Support|GSK: Honoraria|GSK: Support for attending meetings and/or travel|Lilly: Grant/Research Support|New Amsterdam Pharma: Grant/Research Support|Novartis: Grant/Research Support|Pharmalog: Grant/Research Support|Syneos: Grant/Research Support|Winecker Pharma: Grant/Research Support Christine Voors-Pette, MD, QPS Netherlands B.V.: Ex-Employee of QPS Netherlands B.V. Hiwot Amare Hailemariam, MD, PhD, GSK: Salary as GSK employee with stock options|GSK: Stocks/Bonds (Public Company) Caroline Portaels, DVM, 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) Bruno Salaun, PhD, GSK: Salary as GSK employee with stock options|GSK: Stocks/Bonds (Public Company) Silvia Damaso, MSc, GSK: Salary as GSK employee with stock options|GSK: Stocks/Bonds (Public Company) 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) Dominique Descamps, MD, GSK: Salary as GSK employee with stock options|GSK: Stocks/Bonds (Public Company) Judith Hill, Dr., GSK: Salary as GSK employee with stock options|GSK: Stocks/Bonds (Public Company) Corinne Vandermeulen, MD, PhD, 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)