ABRYSVO RSV VACCINE SHOWS LITTLE BENEFIT IN LARGE TRIAL
February 2026
Several adult respiratory syncytial virus (RSV) vaccines have been developed in recent years that are heavily marketed to seniors, with commercials that warn of a miserable death in the local ICU for those who dare to go unvaccinated. Pfizer's bivalent RSV prefusion F protein-based vaccine (Abrysvo®) is approved for adults 60 years and older. A recent large trial evaluated its effectiveness at preventing hospitalization for RSV-related respiratory tract disease.
The DAN-RSV trial was a pragmatic, open-label trial performed in Denmark during the 2024–2025 winter season. 131,379 adults aged 60 years or older (average age 69 years) were assigned in a 1:1 ratio to receive RSVpreF (Abrysvo®) or no RSV vaccine. Baseline and outcome data were collected from national registries. The primary endpoint was hospitalization for RSV-related respiratory tract disease. During follow-up (from 14 days after the scheduled trial visit until May 31, 2025), hospitalization for RSV-related respiratory tract disease occurred in 3 participants in the RSVpreF group and 18 in the control group (0.11 vs. 0.66 events per 1000 participant-years; vaccine effectiveness, 83.3%; 95% CI, 42.9 to 96.9; P=0.007). Hospitalization for RSV-related lower respiratory tract disease occurred in 1 and 12 participants, respectively (vaccine effectiveness, 91.7%; 95% CI, 43.7 to 99.8; P=0.009).
In a study of this size (N>130,000), even the slightest difference in the outcome will be statistically significant, as evidenced by the significant finding despite the small absolute difference in outcome events (15 events). Study weaknesses include the open-label design, which may have affected whether subjects sought care for URI symptoms and/or were hospitalized. The number needed to treat (NNT) to prevent one RSV hospitalization in this study population was approximately 4,400. There was no statistically significant difference in deaths from any cause between the groups (146 in the vaccine group vs. 120 in the control group).
The main takeaway from this study is that RSV is not a significant cause of respiratory illness in older adults residing in Denmark. Widespread vaccination is unlikely to be cost-effective.
