Effectiveness of Nirsevimab in High-Risk Children Under 24 Months for Prevention of Respiratory Syncytial Virus Infection: A Systematic Review and Meta-Analysis

초록

Background: Respiratory syncytial virus (RSV) is a major cause of lower respiratory tract infection (LRTI) in infants. This meta-analysis aims to investigate the real-world effectiveness of nirsevimab, a long-acting monoclonal antibody against RSV, in high-risk children. Methods: We searched PubMed, Embase, the Cochrane Library, and KoreaMed from database inception to August 28, 2025. Studies reporting the effectiveness of nirsevimab in high-risk infants under 24 months of age were included. Infants with underlying comorbidities and preterm infants were considered high-risk. Random-effects models were used to generate pooled effectiveness estimates with 95% confidence intervals (CIs). Results: Seven studies involving 22,418 high-risk children were included: five test-negative or matched case-control studies and two retrospective cohorts, conducted between 2023 and 2024. Studies were conducted primarily in France (n = 4), with one each from Australia, Chile, and Spain. Of the total, 89.4% (n = 20,043) were preterm infants and 10.6% (n = 2,375) had underlying comorbidities. Pooled effectiveness was 71.9% (95% CI, 63.7–80.1; I2 = 9%) against RSV-associated LRTI or hospitalization and 72.4% (95% CI, 63.6–81.2; I2 = 17%) against RSV-related hospitalization. Pooled effectiveness for RSV-related LRTI and hospitalization among preterm infants was 67.8% (95% CI, 59.2–76.5; I2 = 0%). Pooled effectiveness was 82.9% (95% CI, 50.0–115.9; I2 = 75%) against RSV-related hospitalization among infants with comorbidities. Conclusion: Nirsevimab provides substantial protection against RSV-associated LRTI and hospitalization in high-risk infants under 24 months of age, supporting its inclusion in RSV prevention strategies for medically vulnerable children in real-world setting. Trial Registration: PROSPERO Identifier: CRD420251152969 © 2026 The Korean Academy of Medical Sciences. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (https://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

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