BACKGROUND: In 2023, the United States (US) Food and Drug Administration approved two vaccines for the prevention of lower respiratory tract disease caused by respiratory syncytial virus (RSV) in adults aged ≥ 60 years.1,2 These vaccines were also recommended by the Centers for Disease Control and Prevention’s (CDC’s) Advisory Committee on Immunization Practices for use among adults aged ≥ 60 years with shared clinical decision-making (SCDM).3 The SCDM recommendation involves joint decision-making between HCPs and patients, which can pose challenges in implementation.4 Through mid-January 2024, the CDC estimates that nearly 9.1 million older adults received an RSV vaccination during the first season of vaccine availability,5 which may lead to substantial public health benefits. Previous analyses have modeled the potential public health impact of RSV vaccination among older adults assuming the same vaccination coverage as influenza vaccines.6 However, RSV vaccination uptake lags considerably behind influenza vaccination coverage.7 The current study evaluates the potential public health impact of US older adult RSV vaccinations, as well as the additional public health impact that could have been achieved with increased vaccination uptake.
METHODS: A multicohort Markov model estimated RSV cases, healthcare resource use, and complications/deaths for simulations with and without RSV vaccination among US adults aged ≥ 60 years (n=82,862,258). The model used a 1-month cycle length, projecting outcomes over a 3-year time horizon. All population, RSV epidemiology, and healthcare resource use inputs were obtained from publicly available sources and published scientific literature. RSV vaccine efficacy estimates were based on the adjuvanted RSVPreF3 vaccine’s phase 3 clinical trial results through a median follow-up period of 17.8 months, with model inputs projected over 3 years using weighted linear regression analyses.8,9 The analysis assumes one-time vaccination of older adults with the adjuvanted RSVPreF3 vaccine in October. Age-specific RSV vaccination coverage estimates used in the base-case analysis were calculated using age-specific coverage estimates through November 30, 2023 (data on file) and total vaccinations administered through January 13, 2024.10 Resulting age-specific coverage estimates were 4.5%, 12.2%, and 14.6% among adults aged 60-64, 65-74, and ≥ 75 years, respectively. The additional burden of RSV that potentially could have been avoided with increased RSV vaccination uptake was modeled using two scenarios: assuming a 5 percentage point increase in coverage for each age group (60-64 years: 9.5%; 65-74 years: 17.2%; ≥ 75 years: 19.6%) and assuming the same vaccination coverage as for influenza vaccines during the 2022-2023 season (60-64 years: 50.1%; ≥ 65 years: 69.7%).5
RESULTS AND CONCLUSION: In the base-case analysis, nearly 9.1 million older adults received an RSV vaccination, resulting in more than 472,000 avoided symptomatic RSV acute respiratory illness (ARI) cases over 3 years. RSV vaccination is further projected to avoid more than 258,000 outpatient visits, nearly 36,000 hospitalizations, and nearly 3,000 deaths. Assuming a 5 percentage point increase in RSV vaccination coverage would have resulted in 4.1 million additional older adult vaccinations. The model estimates that these vaccinations would have resulted in more than 216,000 additional avoided symptomatic RSV-ARI cases compared to the base case, including nearly 114,000 fewer outpatient visits, more than 14,000 fewer hospitalizations, and more than 1,000 fewer deaths over 3 years. If RSV vaccination uptake had reached the same level as for influenza vaccines, nearly 45 million additional older adults would have been vaccinated, resulting in an additional 2.3 million avoided symptomatic RSV-ARI cases over 3 years compared to the base case. The additional avoided burden would have included more than 1.2 million avoided outpatient visits, nearly 157,000 avoided hospitalizations, and nearly 13,000 avoided deaths. Results from this study provide an initial evaluation of the potential public health impact of RSV vaccination among US older adults, based on uptake estimates through mid-January 2024. RSV vaccinations received during the first season of vaccine availability are projected to substantially reduce RSV burden over the next 3 years. Findings from scenarios of increased uptake highlight the additional impact that RSV vaccinations can have in reducing disease burden.
