Importance Respiratory syncytial virus (RSV) infection is linked to elevated cardiovascular risk, particularly in individuals with preexisting cardiovascular disease (CVD). A bivalent RSV prefusion F protein (RSVpreF) vaccine was recently approved for preventing RSV-related lower respiratory tract illness, but its effectiveness against cardiovascular outcomes has not been evaluated in a randomized trial. Objective To investigate the vaccine effectiveness of RSVpreF compared with no vaccine against cardiovascular outcomes among adults aged 60 years or older. Design, Setting, and Participants Prespecified secondary analysis of the DAN-RSV trial, a pragmatic, open-label, individually randomized clinical trial conducted in Denmark during the 2024-2025 winter season. The first participant was enrolled on November 18, 2024. Adults aged 60 years or older were eligible for inclusion regardless of comorbidity status. Interventions Participants were randomized 1:1 to receive RSVpreF (n = 65 642) or no vaccine (n = 65 634). Main Outcomes and Measures Hospitalization for any cardiorespiratory disease was a prespecified secondary outcome, and hospitalizations for any CVD, heart failure, myocardial infarction, stroke, and atrial fibrillation were prespecified exploratory outcomes. Outcomes were assessed from 14 days after booked study visit through May 31, 2025. Vaccine effectiveness was calculated as 1 − incidence rate ratio, expressed as a percentage. Results Of 131 276 participants included (mean age, 69.4 SD, 6.5 years; 50.3% male), 28 662 (21.8%) had preexisting CVD. All-cause cardiorespiratory hospitalization incidence was lower in the RSVpreF group compared with the control group (26.3 vs 29.2 events per 1000 participant-years PY; absolute rate reduction, 2.90 95% CI, 0.10-5.71 per 1000 PY; vaccine effectiveness, 9.9% 95% CI, 0.3%-18.7%; P = .04). There was no significant interaction by baseline CVD status (CVD at baseline: vaccine effectiveness, 5.0% 95% CI, −11.2% to 16.7%; no CVD at baseline: vaccine effectiveness, 15.2% 95% CI, 2.2%-27.1%; P = .27 for interaction). For the RSVpreF group vs control group, respectively, incidence rates of all-cause cardiovascular hospitalization were 16.4 vs 17.7 events per 1000 PY (vaccine effectiveness, 7.4% 95% CI, −5.5% to 18.8%; P = .24), and incidence rates of stroke were 3.0 vs 3.8 events per 1000 PY (vaccine effectiveness, 19.4% 95% CI, −8.6% to 40.4%; P = .14). There were also no statistically significant between-group differences for myocardial infarction, heart failure hospitalization, and atrial fibrillation. Conclusions and Relevance In adults aged 60 years or older, all-cause cardiorespiratory hospitalization was significantly lower with RSVpreF than with no vaccine. The findings suggest potential downstream cardiorespiratory benefits of RSV immunization, although the effect on all-cause cardiovascular hospitalization was not statistically significant. Trial Registration ClinicalTrials.gov Identifier: NCT06684743
Lassen et al. (Sat,) studied this question.