RSV Vaccine mRNA-1345 Tied to Fewer Infections in Older Veterans

A single dose of the respiratory syncytial virus (RSV) vaccine mRNA-1345 (mRESVIA, Moderna) was associated with protection against RSV illness and related health care use among US veterans 50 years and older during the 2025-2026 respiratory illness season, according to a cohort study published in JAMA Network Open.

The authors noted that clinical trials showed mRNA-1345 protected against RSV illness, but data on how well it works in broader patient populations are still needed.. The Veterans Health Administration (VHA) began preferentially using mRNA-1345 in fall 2025.

Using a target trial emulation framework, the researchers matched 74,926 vaccinated veterans with up to 4 unvaccinated individuals in monthly sequential trials from October 2025 to January 2026 (median age, 73.0 years; 91.3% male). Over a median follow-up of 160 days, estimated vaccine effectiveness against any documented RSV infection, the primary outcome, was 60.3% (95% CI, 49.0%-70.4%). Estimated effectiveness was 60.2% against RSV-associated emergency department or urgent care encounters and 81.8% against RSV-associated hospitalizations, although the hospitalization estimate was imprecise (95% CI, 58.1%-99.9%).

Estimated effectiveness against documented infection decreased with age, from 82.9% in those aged 50 to 59 years to 28.6% in those 80 years or older; for the oldest group, the confidence interval included the possibility of no protection (95% CI, −12.0% to 60.4%). A sensitivity analysis comparing same-day mRNA-1345 and influenza vaccination with influenza vaccination alone yielded similar estimates. The authors noted that few outcome events limited precision, that residual confounding may be present, and that RSV illness treated outside the VHA may have been missed.

The authors concluded that longer follow-up is needed to determine how long protection lasts across multiple seasons and that studies comparing the available RSV vaccines are needed to clarify their relative benefits.

Source: Bui DP, Yan L, Li Y, et al. Effectiveness of the mRNA-1345 vaccine against respiratory syncytial virus in US veterans. JAMA Netw Open. 2026;9(10):e2640981. doi:10.1001/jamanetworkopen.2026.40981