A pragmatic individually randomized trial to evaluate bivalent RSV prefusion F protein–based vaccine effectiveness for preventing RSV hospitalizations in adults aged 60 years or above (DAN-RSV): Rationale and trial design

Abstract

Background: Respiratory syncytial virus (RSV) can cause serious illness in older adults and those with chronic conditions. While the bivalent RSVpreF vaccine has been shown to protect against RSV-related respiratory tract disease, its impact on severe RSV-related and broader cardiorespiratory hospitalizations remains untested in a fully powered randomized trial. This pragmatic, individually randomized, open-label, parallel-group trial aims to evaluate RSVpreF vaccine effectiveness (VE) in reducing the risk of RSV-related and all-cause cardiorespiratory hospitalizations in adults aged 60 and older. Methods: DAN-RSV is randomizing Danish adults 1:1 to receive either RSVpreF or no RSV vaccine. The trial uses nationwide registries for recruitment, where eligible citizens are identified and invited via the national electronic messaging system and can provide electronic informed consent remotely. Baseline, safety, and outcome data are collected through the national health registries using the civil registration number provided at consent. Up to 130,000 participants will be enrolled during the 2024/2025 winter season. The primary objective is to assess vaccine effectiveness (VE) against RSV-related respiratory tract disease hospitalization. Secondary endpoints include RSV-related and all-cause lower respiratory tract disease hospitalizations, RSV-related and all-cause cardiorespiratory hospitalizations, and all-cause death. Conclusion: DAN-RSV is an innovative trial combining the gold standard of individual randomization with pragmatic data collection via centralized health records and national health registries. This design offers a feasible approach to assess the impact of RSVpreF on clinically meaningful cardio-respiratory outcomes in adults ≥60 years in a real-world setting – while minimizing bias through use of randomization. The results will support cost-effectiveness analyses and inform future vaccination policies. Trial registration: NCT06684743, registered November 9, 2024 (https://clinicaltrials.gov/study/NCT06684743)