Peer-reviewed article
Epidemiological Impact of Nirsevimab on Admissions for Bronchiolitis in a Pediatric Emergency Department: A Single-Center Cohort Study.
Emanuele Castagno, Carola Aschieri, Irene Ferri, Sara El Khbazi, Lorenzo Milani et al. ·
Summary
Written by AI, not yet AICS's view · claude-haiku-4-5-20251001This study examined how nirsevimab, a monoclonal antibody for respiratory syncytial virus (RSV), affected bronchiolitis cases in a large Italian children's hospital emergency department. Across two winter seasons, RSV cases dropped significantly when nirsevimab immunization coverage reached 87.5%, with the virus being much less common in vaccinated children. While hospitalization rates remained relatively stable, the absolute number of admissions was cut in half. The findings support using nirsevimab as a standard preventive measure for infants.
Key points
- RSV positivity decreased significantly from 47.9% to 32.4% between the two seasons (p = 0.003)
- Immunized children had much lower RSV positivity (16.2% vs. 51.5% in unimmunized children, p < 0.001)
- Immunization reduced the risk of RSV-positive cases by 84% (OR = 0.159)
- Immunization coverage reached 87.5% by April 2025
- Absolute bronchiolitis admissions were halved despite stable hospitalization rates
Limitations
This is a single-center study in one Italian hospital, so findings may not generalize to other settings or countries with different RSV epidemiology. The study is retrospective and observational, which limits ability to establish causation or account for unmeasured confounders such as changes in testing practices or circulation of other respiratory viruses.
Abstract
Respiratory syncytial virus (RSV) is the leading cause of bronchiolitis in children < 24 months and a major public health concern, causing high rates of Emergency Department (ED) visits, hospitalizations, and Pediatric Intensive Care Unit (PICU) admissions. Nirsevimab is a recombinant monoclonal antibody recommended for all infants and high-risk children < 24 months. A retrospective single-center cohort study was conducted to evaluate the impact of nirsevimab introduction on bronchiolitis epidemiology in an Italian tertiary pediatric ED, accounting for 40,000 admissions/year. All children < 24 months who presented to our ED with bronchiolitis during two consecutive RSV seasons (first season: 1 October 2023 to 30 April 2024; second season: 1 October 2024 to 30 April 2025) were included. Descriptive and multivariate analyses are reported. Overall, 484 patients were analyzed (336 in 2023-2024; 148 in 2024-2025), with immunization coverage reaching 87.5% by April 2025. Compared with the previous season, RSV positivity decreased significantly (32.4% vs. 47.9%; p = 0.003) and was lower in immunized children (16.2% vs. 51.5%; p < 0.001). Immunization was associated with a reduced risk of RSV-positive swab in the second season (OR = 0.159, 95% CI: 0.059-0.397). Among RSV-negative patients, other respiratory viruses increased (p < 0.001), while co-infections increased in RSV-positive cases (p = 0.021). Hospitalization rates remained stable, though absolute admissions were halved. In conclusion, nirsevimab immunization reduced RSV burden, supporting its inclusion in universal prevention programs and the need for multicenter prospective studies to assess long-term outcomes.
Findings the Hub has extracted
Each claim below is labelled by its type of design and links back to this report.
- Intervention
- Nirsevimab immunization, a monoclonal antibody against RSV, administered to all infants and high-risk children under 24 months
- Population
- Children under 24 months presenting to a pediatric emergency department with bronchiolitis across two consecutive RSV seasons (n=484; 336 in season 1, 148 in season 2)
Key finding
RSV positivity decreased significantly from 47.9% to 32.4% (p = 0.003)