Nirsevimab effectiveness on paediatric emergency visits for RSV bronchiolitis: a test-negative design study
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Updated: Jul 9, 2026
An In vitro Model to Study Immune Responses of Human Peripheral Blood Mononuclear Cells to Human Respiratory Syncytial Virus Infection
Published on: December 10, 2013
Lea Lenglart1,2, Corinne Levy3,4,5,6, Romain Basmaci7,6,8
1Paediatric Emergency Department, Robert Debré Hospital, Assistance Publique - Hôpitaux de Paris, 48 Boulevard Sérurier 75019, Paris, France. Lea.lenglart@aphp.fr.
Abstract:
Bronchiolitis is one of the leading reasons for paediatric emergency department (PED) visits. France was one of the few countries in the world to implement nirsevimab during winter 2023-2024 in order to reduce the burden of bronchiolitis each year. We conducted a test-negative design study, including all infants younger than 1, diagnosed with a first episode of bronchiolitis. We included all cases presenting to the PED of five university hospitals across France, between October 1, 2023, and February 29, 2024, and undergoing a nasopharyngeal sample for RSV testing. Case patients were the RSV-positive bronchiolitis and control patients the RSV-negative. As a follow-up, all parents were contacted by e-mail 15 days after inclusion. We included 383 bronchiolitis patients, of which 274 tested positive for RSV (75.2%). Among case patients, 27/274 (9.8%) received nirsevimab, compared to 50/109 (46.2%) among control patients. Nirsevimab had an adjusted estimated effectiveness of 82.5% (95% CI [68.0-90.8]) at PEDs. Sensitivity analyses found similar results. At 15-day follow-up, characteristics were similar between children immunized by nirsevimab or not.
Conclusion:
Our findings advocate for nirsevimab widespread adoption to alleviate the burden of RSV bronchiolitis in paediatric emergency departments.
Trial Registration:
NCT04743609 (date of registration: February 4, 2021).
What Is Known:
• Each year, RSV-bronchiolitis places significant pressure on pediatric emergency services. • France is one of the first countries in the world to have implemented nirsevimab in septembre 2023.
What Is New:
• Nirsevimab effectiveness on pediatric emergency visits for RSV-bronchiolitis has been estimated to 82.5% (95% CI [68.0-90.8]) in our study. • The effectiveness was as strong to prevent hospitalizations and sever illnesses.
