Treatment with nirsevimab has been shown to bring down the number of hospitalizations due to respiratory syncytial virus (RSV) infections and prevent the development of severe disease in infants, according to a study presented at ESPID 2026.
“Nirsevimab is associated with significant reductions in RSV-related hospitalization and severe disease outcomes,” said the study authors led by Dr Myrsini Kopanou, P&A Kyriakou Children’s Hospital, Second Department of Pediatrics, Athens, Greece.
A systematic review and meta-analysis was conducted in accordance with PRISMA guidelines. The databases of PubMed, Embase, Scopus, Cochrane Library, and ClinicalTrials.gov were searched from inception to 25 October 2025. [ESPID 2026, abstract EPV-0256]
Kopanou and colleagues identified randomized controlled trials and observational studies that compared nirsevimab with placebo or no immunization in children aged <2 years. They estimated the pooled relative risks (RRs) with 95 percent confidence intervals (CIs) using random-effects models.
Forty-four studies met the eligibility criteria. Pooled results showed the significant association between nirsevimab use and reductions in the risk of RSV-related hospitalizations (RR, 0.30, 95 percent CI, 0.24‒0.38) and medically attended RSV infection (RR, 0.34, 95 percent CI, 0.25‒0.45).
“Similar reductions were observed across study designs, with the greatest effect observed in randomized [controlled] trials,” Kopanou and colleagues said.
Furthermore, treatment with nirsevimab resulted in a reduced risk of intensive care unit admission (RR, 0.35, 95 percent CI, 0.20‒0.62), supplemental oxygen use (RR, 0.40, 95 percent CI, 0.28‒0.58), and mechanical ventilation (RR, 0.43, 95 percent CI, 0.27‒0.68).
In subgroup analyses, the authors noted generally consistent effectiveness of the study drug across age, gestational age, and comorbidity status. However, estimates were not as accurate in smaller subgroups.
“These findings support [the] effectiveness [of nirsevimab] in both clinical trial and real-world settings and provide evidence to inform immunization strategies in early life aimed at reducing the global burden of RSV,” said Kopanou and colleagues.
Respiratory infections
The findings are consistent with a study in Italy, which found a substantial decrease in paediatric acute respiratory infection (ARI) hospitalizations following the introduction of nirsevimab, thus proving its effectiveness against severe disease. [ESPID 2026, abstract EPV-0336]
In the 2024‒2025 season, overall ARI hospitalizations dropped significantly compared with the two preceding seasons (2022‒2023 and 2023‒2024). This reduction was likely driven by the impact of nirsevimab immunization, according to the investigators led by Dr Susanna Esposito, Parma University Hospital, Pediatric Clinic, Parma, Italy.
“Despite this reduction, RSV remained the most frequently detected virus across all seasons,” said Esposito and her team. “In 2024–2025, RSV monoinfections increased, while RSV coinfections remained stable, and the proportion of RSV-associated hospitalizations relative to total ARI admissions was unchanged.”
These findings lend support to the current study, claiming that “RSV remains a leading cause of acute lower respiratory tract infection and hospitalization in infants, contributing substantially to global healthcare burden.”
Nirsevimab is a long-acting monoclonal antibody providing protection with a single dose throughout the RSV season. It has been recently introduced into clinical practice.
“While evidence from clinical trials and real-world studies suggest high effectiveness, variability across populations and study designs underscores the need for comprehensive evidence synthesis,” Kopanou and colleagues said.