RSV vaccine reduced RSV-related hospitalizations
In adults 60 years or older, a single RSV prefusion F vaccine dose greatly lowered RSV-related hospitalization, with very small absolute risk reduction.
*Pragmatic open-label randomized trial; Level 1b (OCEBM).

Citation

Lassen MCH, Johansen ND, Christensen SH, et al. RSV Prefusion F Vaccine for Prevention of Hospitalization in Older Adults. N Engl J Med. 2026;394:138-151. doi:10.1056/NEJMoa2509810.

Background

Respiratory syncytial virus (RSV) can cause severe winter respiratory illness in older adults, but randomized trial evidence on preventing hospitalization has been limited.

Patients

131,276 adults in Denmark aged 60 years or older. No formal exclusions; routine vaccine contraindications (e.g., severe allergy to components or acute illness on vaccination day) applied.

Intervention

Single dose of bivalent RSV prefusion F protein vaccine.

Control

No RSV vaccine.

Outcome

Primary: hospitalization for RSV-related respiratory tract disease. Secondary: hospitalization for RSV-related lower respiratory tract disease; hospitalization for respiratory tract disease from any cause; serious adverse events.

Follow-up Period

From 14 days after the scheduled visit until May 31, 2025 (one winter season).

Results

Outcome RSV vaccine No vaccine Vaccine effectiveness (95% CI) Approx. NNT
Hospitalization for RSV-related respiratory tract disease (primary) 3/65,642 18/65,634 83.3% (42.9 to 96.9) ~4,374
Hospitalization for RSV-related lower respiratory tract disease 1/65,642 12/65,634 91.7% (43.7 to 99.8) ~5,963
Hospitalization for respiratory tract disease from any cause 284/65,642 335/65,634 15.2% (0.5 to 27.9) ~1,285
CI = confidence interval; NNT = number needed to treat (approximate, based on trial-period risks).
Primary analyses were intention-to-treat. Serious adverse events within 6 weeks were similar (2.1% vaccine vs 2.4% control).

Limitations

RSV-related hospitalizations were very rare, so estimates are based on few events and absolute benefit per person was small (large NNT). RSV testing in routine care was limited, which may have missed RSV-related cases. Open-label design and single-country (Denmark) setting may limit generalizability.

Funding

Pfizer; sponsor helped design/statistics, not trial conduct or data analysis.

Clinical Application

Offer this RSV vaccine to older adults to reduce RSV-related hospitalization; counsel that individual absolute benefit is small, but population benefit may be meaningful.