1630. Clinical Profile of Acute Respiratory Illness (ARI) Events in the Phase 3 Trial The RSV Vaccine Efficacy Study iN Older Adults Immunized against RSV Disease (RENOIR)

BACKGROUND: RENOIR is a phase 3 randomized, double-blinded, placebo-controlled study evaluating Vaccine Efficacy (VE) to prevent lower respiratory tract illness (LRTI) in adults ≥ 60 years of age during 2 RSV seasons in Northern and Southern Hemisphere countries (NCT05035212). End of RSV Season 1 (EoS1) analysis demonstrated VE of 88.9% for RSV-associated Lower Respiratory Tract Illness (LRTI-RSV) with 3+ symptoms, VE of 65.1% for LRTI-RSV with 2+ symptoms, and VE of 62.2% for all Acute Respiratory Illness (ARI)-RSV events including LRTI-RSV 2+ and 3+ events. We sought to understand the ARI symptom distribution (e.g. upper respiratory versus lower) among all RSV confirmed endpoints, and the characterization of medical diagnoses provided for these endpoints by clinicians. METHODS: As per study protocol, ARI is an illness involving 1 or more of 7 respiratory illness symptoms lasting more than 1 day: new/increased sore throat, cough, nasal congestion, nasal discharge, wheezing, sputum production, shortness of breath during the RSV season. Participants with ARI symptoms obtain a nasal self-swab within 7 days of onset for RT-PCR testing and undergo virtual or in-person evaluation. Clinical diagnoses are collected at medically attended visits or by investigator assessment. Additional Study Definitions: LRTI is an ARI with at least 2 or 3 signs/symptoms: new or increased cough, wheezing, sputum production, shortness of breath, tachypnea lasting more than 1 day. ARI-RSV and LRTI RSV is an RT-PCR confirmed ARI or LRTI. RESULTS: At EoS1, respiratory symptoms trended lower for cough, sputum production, wheezing, shortness of breath, and tachypnea in RSVpreF recipients compared to placebo recipients. Of these wheezing, shortness of breath, and tachypnea are considered as more severe symptoms. Diagnoses of bronchitis, Influenza-like illness, and pneumonia were less common in RSVpreF recipients compared to placebo recipients. [Figure: see text] [Figure: see text] CONCLUSION: The reduction of more severe LRTI-RSV symptoms and diagnoses amongst all ARI-RSV events in vaccine recipients reflects the higher VE against more severe RSV disease observed in the RENOIR study. The vaccine impacts symptoms that are associated with lower respiratory involvement. DISCLOSURES: Gonzalo Pérez Marc, M.D., GSK: Grant/Research Support|Merck: Grant/Research Support|Moderna: Expert Testimony|Moderna: Grant/Research Support|Pfizer: Grant/Research Support Edward E. Walsh, MD, Icosavax: Advisor/Consultant|Merck: Advisor/Consultant|Merck: Grant/Research Support|Merck: Honoraria|Moderna: Advisor/Consultant|Pfizer: Grant/Research Support Elliot N. DeHaan, MD, Pfizer: Employee|Pfizer: Stocks/Bonds Agnieszka Zareba, MD PhD, Pfizer: Employee|Pfizer: Stocks/Bonds|Pfizer: Stocks/Bonds Qin Jiang, PhD, Pfizer: Employee|Pfizer: Employee|Pfizer: Stocks/Bonds|Pfizer: Stocks/Bonds Kumar Ilangovan, MD, MSPH, MMCi, Pfizer, Inc.: Employee|Pfizer, Inc.: Stocks/Bonds Daniel P. Eiras, MD, MPH, Pfizer, Inc.: Stocks/Bonds Tarek Mikati, MD,MPH, Pfizer: Stocks/Bonds Elena Kalinina, PhD, Pfizer: Pfizer employee|Pfizer: Stocks/Bonds David Cooper, PhD, Pfizer, Inc.: Stocks/Bonds Annaliesa S. Anderson, PhD, Pfizer: Employee|Pfizer: Stocks/Bonds Kena A. Swanson, Ph.D., Pfizer: Employee|Pfizer: Stocks/Bonds William C. Gruber, MD, Pfizer, Inc.: Employee|Pfizer, Inc.: Stocks/Bonds Alejandra C. Gurtman, M.D., Pfizer: Employee|Pfizer: Stocks/Bonds Beate Schmoele-Thoma, MD, Pfizer: Stocks/Bonds