The Impact of the 2025 Infant and Maternal Respiratory Syncytial Virus (RSV) Prevention Program on RSV-related Hospitalisations in the Australian Capital Territory

Nirsevimab, a novel long-acting monoclonal antibody targeted at RSV became available for vulnerable babies in the Australian Capital Territory (a small jurisdiction in Australia) in April 2024. Maternal RSV vaccine, Abrysvo, became available for all women of 28-36 weeks gestation in February 2025. Through either nirsevimab or Abrysvo, all infants born from 1 January 2025 in the jurisdiction have universal eligibility for RSV immunoprophylaxis. This study will use interrupted time series methodology to evaluate the impact of the 2025 RSV prevention program on RSV-related hospitalisation in children under 2 years of age. Historical data from 2022-2023 will form the pre-nirsevimab period, and 2022-2024 the pre-Abrysvo period. 2025 will form the post-intervention period. Secondary objectives are to: 1. Evaluate the impact of the 2025 RSV prevention program on RSV-related Emergency Department (ED) presentations 2. Evaluate the impact on the reported incidence of RSV