TOPLINE:

The implementation of universal nirsevimab prophylaxis was associated with significantly lower respiratory syncytial virus (RSV) positivity and reduced disease severity, including shorter hospital stays and a lower use of high-level respiratory support, among infants compared with unprotected peers.

METHODOLOGY:

• Researchers conducted a retrospective cohort study to evaluate the real-world impact of universal nirsevimab prophylaxis on the epidemiology and disease severity of paediatric RSV infections.
• They included 758 children (younger than 18 years) presenting with acute respiratory symptoms who underwent nasopharyngeal swab testing with a multiplex polymerase chain reaction at a tertiary care paediatric emergency department in Italy over three consecutive respiratory seasons (October to April) between 2022 and 2025.
• The primary outcome was the seasonal proportion of RSV positivity tests; secondary outcomes included hospitalisation, the length of hospital stay, the need for respiratory support, and ICU admission.

TAKEAWAY:

• RSV-positive cases dropped from a mean of 31.9% in the pre-nirsevimab era (2022-2024) to 19.7% in the nirsevimab era (2024-2025), with a significant reduction observed in infants aged 0-24 months, in whom the rate declined from 44.9% to 19.9% (P < .001).
• Among RSV-positive infants aged 0-12 months, those who received nirsevimab had shorter median hospital stays (6.0 vs 8.5 days) and required lower high-level respiratory support (25.0% vs 58.3%; P ≤ .05 for both) than those who did not receive nirsevimab.
• RSV-positive infants aged 0-6 months who received nirsevimab had a shorter median hospital stay than those who did not receive nirsevimab (5.0 vs 9.5 days; P = .02), and a lower requirement for high-level respiratory support (25.0% vs 62.5%), although this difference was not statistically significant.
• After adjustment, younger age and infection with RSV were independent predictors of severe disease requiring ICU admission or high‑level respiratory support; however, on admission, low saturated oxygen, elevated partial pressure of carbon dioxide, and low pH were significantly associated with severe outcomes (P < .001 for all).

IN PRACTICE:

"This real-world evidence underscores the immense public health value of nirsevimab as a tool to protect infants, reduce hospital stays, and alleviate the significant strain that RSV places on pediatric healthcare systems each winter," the authors wrote.

SOURCE:

This study was led by Alessandra Chiara Ferrari, Paediatrics Unit, ASST Cremona, Maggiore Hospital, Viale Concordia 1, Cremona, Italy. It was published online on January 15, 2026, in the European Journal of Pediatrics.

LIMITATIONS:

The single-centre retrospective design may have limited generalisability and precluded causal inference. Polymerase chain reaction testing, although protocol-guided, may not have been entirely uniform in practice, and the lack of data on key comorbidities limited the adjustment for factors influencing RSV severity.

DISCLOSURES:

This study did not receive any specific funding. The authors declared having no conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.