RSV prefusion F vaccine effectiveness in older adults with immunosuppression: a prespecified analysis of the DAN-RSV trial.
TL;DR
In adults aged 60 years or older, RSVpreF vaccination reduced hospitalisations for RSV-related respiratory tract disease with no statistical evidence of effect modification by immunosuppression status; however, the study was not powered to exclude subgroup differences.
Abstract
Background
Individuals with immunosuppression are at an increased risk of severe respiratory syncytial virus (RSV) disease. We aimed to evaluate the effectiveness of a bivalent RSV prefusion F protein-based vaccine (RSVpreF) in older adults (≥60 years) according to immunosuppression status.
Methods
This study was a prespecified subgroup analysis of a pragmatic, open-label, nationwide randomised clinical trial conducted in Denmark during November-December, 2024. Older adults were randomised 1:1 to a single dose of RSVpreF or no vaccine. Immunosuppression was defined as at least one hospital encounter with an immunosuppressive condition or treatment. Baseline characteristics and outcomes were ascertained from nationwide registries. The primary outcome was hospitalisation for RSV-related respiratory tract disease, defined as respiratory hospitalisation with an RSV diagnosis code or a positive RSV test. Follow-up began 14 days after the scheduled study visit and continued until May 31, 2025.
Findings
Among the 131 276 participants (65 642 RSVpreF; 65 634 no vaccine), 5199 (4·0%) were immunosuppressed. In total, 21 participants were hospitalised with RSV-related respiratory tract disease, seven with immunosuppression, and 14 without immunosuppression. In the no-vaccine group, the incidence of RSV-related respiratory tract disease hospitalisation was more than nine-fold higher in participants with immunosuppression than in participants without (4·68 vs 0·50 events per 1000 person-years). As previously shown, RSVpreF significantly reduced RSV-related respiratory tract disease hospitalisations in the overall population (vaccine effectiveness 83·3% [95% CI 42·9 to 96·9]). No significant effect modification by immunosuppression status was observed (vaccine effectiveness 60·5% [95% CI -141·4 to 96·2] among those with immunosuppression and 92·3% [48·7 to 99·8] among those without immunosuppression; p for interaction=0·22). The point estimate was numerically lower among participants with immunosuppression, with a wide confidence interval crossing the null, but there was no statistical evidence of heterogeneity between subgroups. The estimated absolute rate reduction was 2·83 events per 1000 person-years (95% CI -2·00 to 7·66) among the participants with immunosuppression and 0·46 events per 1000 person-years (0·18 to 0·74) among those without immunosuppression.
Interpretation
In adults aged 60 years or older, RSVpreF vaccination reduced hospitalisations for RSV-related respiratory tract disease with no statistical evidence of effect modification by immunosuppression status; however, the study was not powered to exclude subgroup differences. Given the higher baseline risk of RSV-related hospitalisation observed among the individuals with immunosuppression, prioritising RSV vaccination in this group with high risk of severe RSV disease could have clinical benefits. The results of this trial could help to inform clinical guidance and vaccination policy, pending confirmation in larger studies.
Funding
The Danish respiratory syncytial virus trial was supported by Pfizer.
