A LARGE international trial has found that a single dose of the RSVPreF3 OA vaccine offers strong and sustained protection against respiratory syncytial virus (RSV)-related lower respiratory tract disease (RSV-LRTD) in older adults across three consecutive RSV seasons.
The Phase 3 AReSVi-006 trial was a randomised, observer-blind, placebo-controlled study conducted at 275 sites across 17 countries. Adults aged 60 years or older were assigned to receive either one dose of RSVPreF3 OA or a placebo before their first RSV season. Prior to the second season, vaccine recipients were re-randomised to receive either a second dose or placebo, while those in the original placebo group received a second placebo. Efficacy was evaluated over three seasons, with specific attention to RSV subtypes A and B, and to high-risk subgroups including older age brackets, those with pre-frailty, and those with underlying health conditions.
Among more than 24,000 participants (12,468 vaccine and 12,498 placebo recipients), a single dose of RSVPreF3 OA demonstrated 62.9% efficacy (97.5% CI: 46.7–74.8) against RSV-LRTD over three seasons, with subtype-specific efficacy of 69.8% against RSV A and 58.6% against RSV B. Efficacy was consistent across age and risk groups, though it declined over time. Revaccination after 1 year did not significantly improve protection compared to a single dose.
The vaccine was well tolerated, with serious adverse events judged related to the trial intervention in fewer than 1% of participants in any group. Five deaths were considered related to the trial intervention, three in the vaccine arms and two in the placebo arm, with no pattern indicating an excess risk.
The results support the use of RSVPreF3 OA in older adults to reduce RSV-LRTD risk over multiple seasons. Further studies are needed to clarify if, and when, revaccination might enhance or extend protection.
Reference
Ison MG et al. Efficacy, safety, and immunogenicity of the AS01E-adjuvanted respiratory syncytial virus prefusion F protein vaccine (RSVPreF3 OA) in older adults over three respiratory syncytial virus seasons (AReSVi-006): a multicentre, randomised, observer-blinded, placebo-controlled, phase 3 trial. Lancet Respir Med. 2025; DOI: https://doi.org/10.1016/S2213-2600(25)00048-7.
