224. Immunosuppression and RSV Prefusion F Protein Vaccine Effectiveness in Older Adults: A Prespecified Subanalysis from the DAN-RSV Trial

TL;DR

This study found that an RSV prefusion F protein vaccine reduced hospitalizations for RSV-related diseases in older adults, including those with weakened immune systems.

Contribution

The study provides evidence that the RSVpreF vaccine is effective in reducing hospitalizations in immunosuppressed older adults.

Findings

RSVpreF reduced RSV-related hospitalizations in immunosuppressed individuals by 60.5%.

The vaccine showed consistent effectiveness across both immunosuppressed and non-immunosuppressed groups.

Hospitalization rates for RSV-related disease were over nine times higher in unvaccinated immunosuppressed individuals.

Abstract

Immunosuppressed (IS) individuals are at high risk of severe respiratory syncytial virus (RSV) complications. This prespecified analysis of DAN-RSV evaluated the effectiveness of a bivalent RSV prefusion F protein-based vaccine (RSVpreF) in preventing RSV-related and all-cause cardio-respiratory hospitalizations among individuals with and without IS.Table 1.Baseline characteristics according to immunosuppression status.Values are presented as mean ± SD or n (%) with p-values from t-test or Pearson chi-squared test.Figure 1.Hospitalization rates according to immunosuppression status in the overall study population.P-values from Poisson regression models.

Baseline characteristics according to immunosuppression status.

Values are presented as mean ± SD or n (%) with p-values from t-test or Pearson chi-squared test.

Hospitalization rates according to immunosuppression status in the overall study population.

P-values from Poisson regression models.

The DAN-RSV trial was a pragmatic, open-label randomized clinical trial conducted during the 2024/25 northern hemisphere winter. Adults aged ≥60 years were enrolled (Nov-Dec 2024) and randomized 1:1 to RSVpreF or no vaccine; only the RSVpreF arm were required to attend a study visit. Baseline and outcome data were obtained from nationwide registries. IS was defined using ICD10 or procedure codes and required ≥1 hospital encounter . Follow-up was from 14 days after vaccination/scheduled visit until May 31, 2025. The primary endpoint was hospitalization for RSV-related respiratory tract disease (RTD); secondary endpoints included hospitalizations for any respiratory and cardio-respiratory disease.Figure 2.Vaccine effectiveness of RSVpreF compared with no vaccine according to immunosuppression status.Vaccine effectiveness was calculated as (1-incidence rate ratio*100%. Interaction p-values were estimated using a Poisson model with a sub-group-by-randomized treatment interaction term included. Abbreviations: PY = person-years; RSVpreF = respiratory syncytial virus prefusion F protein-based vaccine; VE = vaccine effectiveness.

Vaccine effectiveness of RSVpreF compared with no vaccine according to immunosuppression status.

Vaccine effectiveness was calculated as (1-incidence rate ratio*100%. Interaction p-values were estimated using a Poisson model with a sub-group-by-randomized treatment interaction term included. Abbreviations: PY = person-years; RSVpreF = respiratory syncytial virus prefusion F protein-based vaccine; VE = vaccine effectiveness.

Among 131,276 participants (65,642 RSVpreF; 65,634 no vaccine), 5,199 (4.0%) were IS. IS participants were older with more comorbidities (Table 1), as well as higher hospitalization rates (Fig. 1). Among the unvaccinated group, RSV-related RTD hospitalization rates were >9 times higher among IS persons (9.26; 4.96/0.5) (Fig. 2). Incidence of RSV-related RTD was lower in the RSVpreF group than in the no-vaccination group, with consistent effects regardless of baseline IS status (1.85 events vs. 4.68 events per 1000 person-years (PY); vaccine effectiveness (VE) 60.5% [95% CI: -147.3 to 96.1] in participants with IS compared with 0.04 events vs. 0.50 events per 1000 PY; VE 92.3% [95% CI: 48.8 to 99.8] in those without; pinteraction = 0.22). Consistent beneficial effects on hospitalization rates for were observed in the RSVpreF group vs no vaccine for other outcomes (p for interaction >0.05 for all).

In adults ≥60 years, RSVpreF vaccination reduced hospitalizations for RSV-related cardio-respiratory disease, with consistent effects across immunosuppression subgroups. High rates of severe RSV related disease support the need for vaccination in this population.

All Authors: No reported disclosures

Figures