Effectiveness of nirsevimab in preventing RSV-hospitalisation among young children in Western Australia 2024
- PMID: 40074179
- DOI: 10.1016/j.jinf.2025.106466
Effectiveness of nirsevimab in preventing RSV-hospitalisation among young children in Western Australia 2024
Abstract
Background: Respiratory Syncytial Virus (RSV) causes a significant burden of illness for children under 2 years of age. Nirsevimab, a long-acting monoclonal antibody, was registered for RSV prevention in Australia in 2023. In April 2024, Western Australia (WA) launched the country's first state-wide nirsevimab program for all infants and high-risk children entering their second RSV season. This study describes the effectiveness of nirsevimab against RSV hospitalisation over a single epidemic season.
Methods: Between April and October 2024, children hospitalised with laboratory-confirmed RSV-associated acute respiratory infection (ARI) and test-negative controls were enrolled from three hospitals in WA. Demographic variables, medical risk factors, symptoms and outcomes were assessed. Nirsevimab effectiveness in preventing RSV-associated hospitalisation was estimated.
Results: Over 7 months, 284 children eligible for nirsevimab were enrolled including 184 RSV positive cases and 100 controls. Coverage of nirsevimab in RSV cases was 22.8% and 60.0% in controls. The overall adjusted effectiveness of nirsevimab against RSV-associated ARI hospitalisation was 88.2% (95% CI: 73.5, 94.7). RSV infection occurred in 42 (22.8%) children who had received nirsevimab; there was no significant difference in RSV illness severity among those immunised and unimmunised.
Conclusion: Nirsevimab was highly effective at preventing RSV-associated ARI hospitalisation in young children in the southern hemisphere.
Summary: This study is the first Australian study to provide nirsevimab effectiveness estimate against RSV hospitalisation over a single epidemic season. The adjusted estimate of nirsevimab effectiveness against RSV-associated ARI hospitalisation was 88.2%, similar to those reported from Northern Hemisphere countries.
Keywords: Children; Effectiveness; Hospitalisation; Immunisation; Nirsevimab; Real-world; Respiratory syncytial virus.
Copyright © 2025 The Author(s). Published by Elsevier Ltd.. All rights reserved.
Conflict of interest statement
Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: UW received travel and accommodation support to attend meetings from Pfizer and Moderna (not related to this study) and has institutional payment for conduct of sponsored multicenter RSV vaccine trial in infants (Moderna). HCM has received institutional honoraria for participation in advisory group meetings on RSV epidemiology from Merck Sharp and Dohme, Pfizer and Evohealth. HCM and PR are in receipt of research funds from an Investigator-Initiated Studies Program of Merck Sharp & Dohme (Australia) Pty Ltd (not related to this study). HCM is in receipt of research funds from Sanofi-Aventis (Australia) (not related to this study). PR has institutional payment for conduct of sponsored multicentre RSV monoclonal antibody studies (Merck Sharp& Dohme, Astra Zeneca/ Medimmune) and RSV maternal vaccine studies (Pfizer, Glaxo Smith Kline). PR has received support to attend international conferences from ReSVinet Foundation and GlaxoSmithKline. PR has received institutional honoraria for participation in advisory board meetings from Clover Biopharmaceuticals, Pfizer, Astra Zeneca, GlaxoSmithKline, Sanofi and Merck Sharpe & Dohme. All other authors declared no conflict of interest.
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