P-683. What if Adult RSV Vaccine Uptake in the US was High Like in Scotland? Missed Opportunities to Reduce Public Health and Economic Burden of RSV

Abstract Background Since June 2024, the United States (US) Advisory Committee on Immunization Practices has recommended routine vaccination against respiratory syncytial virus (RSV) for all adults aged ≥ 75 years. Despite the recommendation, uptake of RSV vaccine among those aged ≥ 75 years remains low, especially compared with other countries that have similar recommendations. We therefore evaluated the potential public health and economic impact of improving vaccine coverage among US adults aged ≥ 75 years, based on observed uptake within the same age group in Scotland. Public health outcomes associated with alternative vaccination strategies for US adults aged ≥75 years Methods We developed a cohort model to depict public health and economic outcomes associated with RSV and the single-season impact of routine immunization with RSV vaccines available during the first season. Severe public health outcomes included RSV episodes requiring hospitalizations (RSV-H) or emergency department (ED; RSV-ED) care, respectively, and RSV hospitalization-associated deaths; economic outcomes included costs associated with medical care for RSV. Vaccine effectiveness (vs. RSV-H: 79%, vs. RSV-ED: 78%) was based on real-world observational data from the 2023-24 RSV season in the US. Two different uptake scenarios were considered: Scenario 1 (23.6%, based on US uptake) and Scenario 2 (68.6%, based on uptake in Scotland). Results With Scenario 1 (23.6% uptake), there were 83,469 RSV-H episodes, 54,864 RSV-ED episodes, and 8,713 RSV-related deaths; associated medical care costs totaled $2.3 billion. With Scenario 2 (68.6% uptake), there were 46,326 RSV-H episodes, 30,823 RSV-ED episodes, and 4,836 RSV-related deaths; associated medical care costs totaled $1.3 billion, representing 44% reductions in all public health and economic outcomes in a single season. Conclusion Findings suggest that if uptake of RSV vaccine among US adults aged ≥ 75 years was comparable to uptake in Scotland, nearly 40,000 additional hospitalizations, 25,000 additional RSV-ED visits, and 4,000 additional RSV-related deaths could have been prevented in the first season following vaccine administration. The US should improve targeted efforts to reach remaining unvaccinated eligible adults to prevent severe outcomes. Disclosures Reiko Sato, PhD, Pfizer Inc: Stocks/Bonds (Public Company) Erica Chilson, PharmD, Pfizer Inc: Stocks/Bonds (Public Company) Erin Quinn, BS, Pfizer Inc: Advisor/Consultant Ahuva Averin, MPP, Pfizer Inc: Grant/Research Support