Effectiveness of Nirsevimab on Primary Care Visits for Respiratory Syncytial Virus-Associated Acute Otitis Media in Infants.

Abstract

To estimate the effectiveness of nirsevimab against respiratory syncytial virus (RSV)-associated acute otitis media (AOM) in ambulatory care. We conducted a test-negative design study, post hoc analysis using data from the prospective Oursyn study involving 37 primary care pediatricians across France from 2020 to 2025. Nasopharyngeal sampling for RSV was performed in infants younger than 1 year diagnosed with AOM during the first 2 RSV seasons with introduction of nirsevimab passive immunization (October 2023 to February 2024 and October 2024 to January 2025). The main outcome of the study was the detection of RSV status in infants with AOM. We performed a multivariable logistic regression with nirsevimab adjusted for age, sex, underlying chronic condition, prematurity, type of childcare, month, year, and geographic region of inclusion. Sensitivity analyses were performed as well. A total of 236 AOM events were included over the study period: 141 during the first season of nirsevimab implementation and 95 during the second season. Among infants with AOM, 41 (29.1%) and 15 (15.8%), respectively, tested positive for RSV. Nirsevimab-adjusted effectiveness was estimated to be 78.2% (95% CI 44.4-92.4) for the prevention of RSV-AOM in this sample. Sensitivity analyses found similar results. These findings highlight the broader protective effect of nirsevimab on complications of respiratory tract infections in infants. NCT04743609.