OBJECTIVES: Respiratory Syncytial Virus (RSV) is a major cause of lower respiratory tract disease (LRTD) and can result in significant morbidity and mortality in older adults. An mRNA-based RSV vaccine, mRNA-1345, has demonstrated efficacy against RSV-LRTD and RSV-acute respiratory tract disease (ARD) in adults aged ≥60 years. The study objective was to estimate potential clinical impact of vaccination with mRNA-1345 in older adults (≥65 years).

METHODS: A static decision-analytic model was used to estimate health outcomes of RSV infections, comparing no vaccination to a single dose of mRNA-1345 over a 2-year timeframe. Base-case analysis assumed a vaccination coverage rate (VCR) of 54% (similar to 2023-24 VCR for flu in French adults ≥65 years). Key epidemiological and vaccine inputs were obtained from published literature and phase 2/3 clinical trial results for mRNA-1345 (18.8 months of median follow up). Vaccine efficacy of mRNA-1345 against RSV-ARD, RSV-LRTD, and associated hospitalizations, were adjusted by French seasonality data and outcomes assessed over a two-year protection period. Outcomes included number of RSV-ARD and RSV-LRTD cases, RSV-LRTD hospitalizations, in-hospital deaths, and numbers needed to vaccinate (NNV) to prevent each of these outcomes. Uncertainty was assessed through sensitivity analyses.

RESULTS: Compared to no vaccination, vaccination with one dose of mRNA-1345 would result in 641,100 fewer symptomatic RSV-ARI cases (including 168,430 RSV-LRTD cases), 17,750 (36%) fewer RSV-related hospitalizations and 3,240 (35%) fewer RSV-related deaths over two years. NNV to prevent one RSV-ARD case was 12; NNVs to prevent one RSV-LRTD case, hospitalization, and death were 47, 448 and 2,456, respectively. A considerable public health impact was observed across a range of sensitivity analyses.

CONCLUSIONS: These findings highlight the potential of mRNA-1345 to substantially reduce RSV disease burden among French older adults aged ≥ 65 years, with model-predicted reductions of 36% for RSV-LRTD hospitalizations and deaths compared to no vaccination.