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Effectiveness of nirsevimab in preventing RSV-hospitalisation among young children in Western Australia 2024
Ushma Wadia1, Hannah C Moore2, Peter C Richmond3
1Department of Infectious Diseases, Perth Children's Hospital, Nedlands, Western Australia, Australia; Department of General Paediatrics, Fiona Stanley Hospital, Murdoch, Western Australia, Australia; Wesfarmers Centre for Vaccines and Infectious Diseases, The Kids Research Institute Australia, Nedlands, Western Australia, Australia; School of Medicine, University of Western Australia, Nedlands, Western Australia, Australia.
Insights
Nirsevimab, a new antibody, proved highly effective in preventing Respiratory Syncytial Virus (RSV) hospitalizations in Australian infants. This study confirms its significant protection against RSV-associated acute respiratory infection in young children.
Area of Science:
- Pediatrics
- Immunology
- Public Health
Background:
- Respiratory Syncytial Virus (RSV) poses a significant health risk to young children.
- Nirsevimab, a long-acting monoclonal antibody, is approved for RSV prevention in Australia.
- Western Australia initiated a nirsevimab program for infants in April 2024.
Purpose of the Study:
- To evaluate the effectiveness of nirsevimab in preventing RSV hospitalizations in infants.
- To assess nirsevimab's impact during the first single epidemic season of its statewide program.
Main Methods:
- Children hospitalized with RSV-associated acute respiratory infection (ARI) and controls were enrolled in Western Australia.
- Data collected included demographics, risk factors, symptoms, and outcomes.
- Nirsevimab effectiveness against RSV hospitalization was estimated using adjusted models.
Main Results:
- 284 children were enrolled; 184 had RSV, 100 were controls.
- Nirsevimab coverage was 22.8% in RSV cases and 60.0% in controls.
- Adjusted nirsevimab effectiveness against RSV-associated ARI hospitalization was 88.2% (95% CI: 73.5, 94.7).
Conclusions:
- Nirsevimab demonstrated high effectiveness in preventing RSV-associated acute respiratory infection hospitalizations in young children.
- This study provides the first Australian effectiveness estimate for nirsevimab, aligning with international findings.
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.
