Real-world effectiveness of nirsevimab against respiratory syncytial virus disease in infants: a systematic review and meta-analysis.

Abstract

Nirsevimab was approved in 2023, and implemented in all-infant immunisation programmes in several high-income countries to prevent lower respiratory tract infection (LRTI) caused by respiratory syncytial virus (RSV). Knowledge of real-world effectiveness of broad nirsevimab programmes is crucial to validate the benefits observed in clinical trials and guide immunisation policy. We assessed the real-world effectiveness of nirsevimab in populations where infant immunisation programmes were introduced. For this systematic review and meta-analysis, we searched MEDLINE, Embase, Web of Science, Scopus, Global Health, and medRxiv from Jan 1, 2023, to Feb 25, 2025, to identify observational studies of immunisation programmes for infants aged 2 years or younger in routine clinical practice reporting original data for the real-world effectiveness of nirsevimab. The primary analysis focused on infants aged 12 months or younger. Pooled analyses were done with inverse-variance random-effects models for RSV-related hospital admissions, intensive care unit (ICU) admissions, and RSV-related LRTI incidence. For length of hospital stay, we used a restricted maximum likelihood random-effects model to estimate the weighted mean difference (WMD) in days between the nirsevimab and control groups. This study is registered with PROSPERO (CRD42024628782). We identified and screened 1238 records, of which 32 cohort and case-control studies from five countries (France, Italy, Luxembourg, Spain, and the USA) were included in the systematic review and 27 of them were included in the meta-analysis. Nirsevimab was associated with a lower odds of RSV-related hospitalisation (odds ratio 0·17; 95% CI 0·12-0·23; I²=85·8%), a lower odds of ICU admission (0·19; 0·12-0·29; 55·6%), and a lower odds of LRTI incidence (0·25; 0·19-0·33; 35·1%) in infants aged 0-12 months. However, length of hospital stay did not differ between the nirsevimab and control groups (WMD 0·01; 95% CI -0·63 to 0·65; I²=62·3%). Our findings indicate that the benefits of nirsevimab observed in clinical trials are also evident in real-world settings, effectively reducing the burden of RSV disease in infants and, consequently, health-care use. Natural Sciences and Engineering Research Council of Canada and the Canadian Immunization Research Network.