Peer-reviewed article
The Impact of Limited-Eligibility Nirsevimab on Paediatric Respiratory Syncytial Virus (RSV) Infection and Hospitalisations in the Australian Capital Territory: An Observational Cohort Study.
Irwin N, Ey S, Chen X, Raina D, Richardson D ·
Summary
Written by AI, not yet AICS's view · claude-haiku-4-5-20251001This study evaluated the impact of a limited-eligibility nirsevimab program (a monoclonal antibody against respiratory syncytial virus) in the Australian Capital Territory from 2022 to 2025. Among 2,355 infants with confirmed RSV, 308 received nirsevimab, primarily those born prematurely, and only 2.4% experienced breakthrough RSV infection. Hospitalizations among the highest-risk infants decreased after the program started, with shorter hospital stays and less need for respiratory support. However, Aboriginal and Torres Strait Islander infants remained over-represented in hospital admissions and were under-served by the program.
Key points
- Only 2.4% of nirsevimab-treated infants experienced breakthrough RSV infection
- Age and prematurity profile of hospitalized infants changed post-nirsevimab, with fewer very young and premature infants admitted
- Length of hospital stay reduced by 8 hours and respiratory support needs fell by one-fifth in the post-program period
- Aboriginal and Torres Strait Islander infants remained over-represented in hospital admissions despite the program
- Overall RSV incidence increased post-nirsevimab (89.06 versus 67.99 per 1,000 infant-years), consistent with local and national trends
Limitations
This is an observational cohort study without a randomized comparison group, so causality cannot be definitively established. The study does not explain why Aboriginal and Torres Strait Islander infants were under-served by the program or explore the reasons for the overall increase in RSV incidence.
Abstract
Aim To assess changes in Respiratory Syncytial Virus (RSV) epidemiology and hospitalisations following implementation of a limited-eligibility nirsevimab program. Methods This observational cohort study included all infants aged < 2 years residing in our jurisdiction with laboratory-confirmed RSV and/or receipt of an RSV monoclonal antibody between April 2022 and March 2025. Cases were followed for emergency department (ED) presentations and hospital admissions. Primary outcomes were RSV incidence, ED presentation, and hospitalisation rates. Results We identified 2355 RSV cases, with 1625 infants presenting to ED and 701 hospitalised. Among 308 infants receiving nirsevimab, the most common indication was prematurity; 2.4% experienced breakthrough RSV infection. RSV incidence increased post-nirsevimab (April 2024-March 2025: 89.06/1000 infant-years) compared with the pre-nirsevimab period (April 2022-March 2024: 67.99/1000 infant-years), consistent with local and national trends. Characteristics of hospitalised infants changed in the post-nirsevimab period: age increased (from 9.4 to 10.7 months, p = 0.019), the proportion aged < 3 months decreased (from 27.6% to 19.7%, p = 0.013) and prematurity prevalence nearly halved (from 13.3% to 7.3%, p = 0.041). Clinical characteristics also changed, with an 8-h reduction in length of stay (p = 0.010), and a one fifth reduction in the need for respiratory support (p < 0.001). No significant differences were observed for Aboriginal and Torres Strait Islander infants. Conclusions Hospitalisations among infants at greatest risk for severe RSV disease reduced following introduction of the limited-eligibility nirsevimab program. However, Aboriginal and Torres Strait Islander infants remained over-represented in hospital admissions and under-served by the program in its first year, warranting further investigation.
Findings the Hub has extracted
Each claim below is labelled by its type of design and links back to this report.
- Intervention
- Limited-eligibility nirsevimab program (monoclonal antibody against RSV) targeting high-risk infants, primarily those born prematurely
- Population
- Infants aged less than 2 years residing in the Australian Capital Territory; 308 received nirsevimab with prematurity as the most common indication
Key finding
Among 308 infants receiving nirsevimab, 2.4% experienced breakthrough RSV infection
N et al. · Europe PMC · 6 May 2026