Nirsevimab is a long-acting monoclonal antibody introduced in 2023 for the prevention of respiratory syncytial virus (RSV)– associated lower respiratory tract infections (LRTIs) in infants. While its efficacy against RSV has been well established in clinical trials, evidence on its broader real-world impact on respiratory-related healthcare use has been limited.
To address this, researchers led by Dewan Md. Sumsuzzman from the Agent-Based Modelling Laboratory at York University, Toronto, conducted a large meta-analysis of post-licensure observational studies to assess whether nirsevimab is associated with reductions in respiratory-related hospitalizations and emergency department visits beyond those caused by RSV alone.
The investigators systematically searched MEDLINE, Embase, Web of Science, Scopus, Global Health, and medRxiv for relevant studies published between January 2023 and June 2025. Eligible studies included postlicensure observational research reporting real-world effectiveness of nirsevimab immunization programs in infants and children aged 24 months or younger. Data extraction and quality assessment were independently performed by two reviewers using the Joanna Briggs Institute Critical Appraisal Checklist, and pooled estimates were generated using random-effects meta-analysis.
Key Findings:
- Of the 1,752 records screened, 15 studies fulfilled the inclusion criteria, with 11 studies from five countries included in the quantitative meta-analysis.
- The pooled analysis covered 263,755 infants and young children, including 236,764 who received nirsevimab and 27,522 in the control groups.
- Nirsevimab use was associated with a 62% reduction in hospitalizations related to all-cause lower respiratory tract infections.
- A 48% reduction was observed in all-cause LRTI–related emergency department visits among infants who received nirsevimab.
- The strongest protective effect was seen for RSV-related outcomes, with a 76% reduction in RSV-associated LRTI emergency department visits.
- Pooled odds ratio analysis showed significantly lower odds of all-cause LRTI–related hospitalization in the nirsevimab group compared with controls.
- Similar significant reductions were noted for all-cause LRTI–related emergency department visits and RSV-related LRTI emergency department visits.
- No statistically significant difference was found between nirsevimab and control groups for all-cause hospitalizations, indicating that the benefit was specific to respiratory-related conditions.
The authors noted that RSV often contributes to severe respiratory illness either directly or by exacerbating other infections. Preventing RSV through nirsevimab may therefore reduce downstream respiratory complications that lead to hospital or emergency care, even when RSV is not identified as the sole cause. These findings highlight the potential of nirsevimab to reduce respiratory morbidity and healthcare utilization in early childhood.
Overall, the study supports the real-world effectiveness of nirsevimab in lowering LRTI-related hospitalizations and emergency department visits in infants and young children. The authors conclude that these results provide important evidence to inform pediatric immunization policies and strengthen the role of nirsevimab in protecting infants during critical early life respiratory seasons.
Reference:
Sumsuzzman DM, Shi C, Langley JM, Moghadas SM. Nirsevimab Against Hospitalizations and Emergency Department Visits for Lower Respiratory Tract Infection in Infants: A Meta-Analysis. JAMA Pediatr. Published online December 22, 2025. doi:10.1001/jamapediatrics.2025.5280
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