Infant respiratory syncytial virus (RSV) immunisation coverage in an Australian regional area, 1 May 2024 - 31 October 2025.

The recent introduction in Australia of respiratory syncytial virus (RSV) immunisations - nirsevimab (neonatal) and Abrysvo (antenatal) - offers potential to reduce the RSV burden in infants. A retrospective cohort study included all infants born at Sunshine Coast University Hospital between 1 May 2024 and 31 October 2025. Of 5,116 infants, 71.7% (3,669/5,116) received valid RSV immunisation: 45.2% through nirsevimab only and 26.4% through antenatal Abrysvo only. During May-December 2024, RSV coverage was achieved exclusively through neonatal nirsevimab. Following Abrysvo's introduction in January 2025, a progressive shift in immunisation composition occurred: among RSV-vaccinated infants, the proportion protected through nirsevimab alone fell from 100% in December 2024 to 13.5% by October 2025, while those protected by Abrysvo alone rose correspondingly from 0% to > 85.0%. Overall RSV coverage remained stable throughout the study period (66.2-77.9%) and throughout the transition period January-October 2025 (66.2-74.9%). Coverage was comparable to Australian and United States estimates but lagged European benchmarks. Abrysvo's introduction maintained rather than improved population-level protection. These findings highlight the need to investigate barriers to RSV immunisation uptake to optimise infant protection.