Unequal impact of respiratory syncytial virus immunization in patients attending Spanish pediatric emergency departments

Abstract

Objectives. To evaluate the impact of respiratory syncytial virus (RSV) prophylaxis with nirsevimab during its 2nd year of administration and analyze the differences between the different strategies implemented across Spanish autonomous communities (ACs) during the current epidemic season. Methods. We conducted a retrospective analytical study with 15 pediatric emergency departments across 9 ACs. We included all infants younger than 6 months who were treated in November, December, and January during 5 epidemic seasons (2018–2019, 2019–2020, 2022–2023, 2023–2024, and 2024–2025). Results. Compared with the average of epidemic seasons prior to the introduction of nirsevimab, in 2024–2025 there was a 65.5% decrease in episodes of acute bronchiolitis (95% CI, 64.3–63.7; P