Peer-reviewed article
Effectiveness of nirsevimab in preventing RSV-hospitalisation among young children in Western Australia 2024.
Wadia U, Moore HC, Richmond PC, Levy A, Bell L et al. ·
Summary
Written by AI, not yet AICS's view · claude-haiku-4-5-20251001This study evaluated nirsevimab, a monoclonal antibody, for preventing hospitalisation from Respiratory Syncytial Virus (RSV) in young children in Western Australia during 2024. Researchers compared children hospitalised with confirmed RSV infection to test-negative controls and measured how many had received nirsevimab. The intervention showed high effectiveness at preventing RSV-associated hospitalisation, with similar results to studies from other countries.
Key points
- Nirsevimab had 88.2% effectiveness against RSV-associated hospitalisation (95% CI: 73.5, 94.7)
- Coverage was 22.8% among RSV cases and 60.0% among controls
- Even children who received nirsevimab and developed RSV infection experienced no significant difference in illness severity compared to unimmunised children
- This was the first Australian study to measure nirsevimab effectiveness during a complete RSV epidemic season
- Results are comparable to effectiveness estimates from Northern Hemisphere countries
Limitations
The study measured effectiveness over a single epidemic season in one Australian state, so results may not generalise to other regions or time periods. The relatively low coverage of nirsevimab among RSV cases (22.8%) limits the strength of conclusions about real-world program impact.
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.