RT Journal Article T1 Respiratory syncytial virus–related lower respiratory tract infection hospitalizations in infants receiving nirsevimab in Galicia (Spain): the NIRSE‑GAL study A1 Manzanares, Ángela A1 Pardo Seco, Jacobo José A1 Rivero Calle, Irene A1 Dacosta Urbieta, Ana Isabel A1 Mallah, Narmeen A1 Rodríguez-Tenreiro Sánchez, Carmen A1 Salas Ellacuriaga, Antonio A1 Martinón Torres, Federico K1 Respiratory syncytial virus (RSV) K1 Low respiratory tract infection (LRTI) K1 Nirsevimab K1 Breakthrough cases K1 Immunization K1 Infants AB As part of the NIRSEGAL study (https://www.nirsegal.es/en), we present the clinical characteristics and course of respiratory syncytial virus (RSV)-related low respiratory tract infection (LRTI) hospitalizations in infants eligible for nirsevimab administration during the 2023–2024 season. Infants eligible for nirsevimab immunization (born between 1 April, 2023, and 30 March, 2024) who were hospitalized due to RSV-related LRTI between September 25, 2023, and April 15, 2024, in a hospital from the Galician Public Health system were included. Clinical and demographic characteristics of RSV-related LRTI hospitalizations were analyzed, with comparisons made between breakthrough cases (those immunized with nirsevimab) and non-breakthrough cases. During the study period, 69 RSV-related LRTI hospitalizations were recorded, with a median hospital stay of 4 (interquartile range (IQR) 3–6) days; 65.2% (N=45) were breakthrough cases. The median age was 2.7 (IQR 1.5–5.2) months, and more than half of them (N=39, 56.5%) were male. The incidence of cases was parallel to the RSV epidemic curve, suggesting no waning of nirsevimab efcacy. Of the total hospitalizations, 16 infants (23.2%) had a high-risk condition, 44 (63.8%) needed oxygen support, 15 (21.7%) were admitted to the intensive care unit (ICU), and 11 (15.9%) received non-invasive mechanical ventilation (NIMV). No statistically signifcant diferences were observed in these characteristics when comparing breakthrough and non-breakthrough cases. Conclusion: In the nirsevimab era, a substantial proportion of children who were hospitalized for RSV-related LRTI needed oxygen support, NIMV, and ICU admission. Clinical characteristics, timing, and outcomes were comparable between breakthrough and non-breakthrough cases. Trial registration: The NIRSE-GAL study protocol was registered on ClinicalTrials.gov (NCT06180993). PB Springer SN 0340-6199 YR 2025 FD 2025-05-02 LK https://hdl.handle.net/10347/42474 UL https://hdl.handle.net/10347/42474 LA eng NO Manzanares, A., Pardo-Seco, J., Rivero-Calle, I. et al. Respiratory syncytial virus–related lower respiratory tract infection hospitalizations in infants receiving nirsevimab in Galicia (Spain): the NIRSE-GAL study. Eur J Pediatr 184, 321 (2025). https://doi.org/10.1007/s00431-025-06151-3 NO Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. The NIRSE-GAL study (CEIC 2023–377, ClinicalTrials.gov number NCT06180993) is partially funded by Sanof/AstraZeneca through a research grant to the Healthcare Research Institute of Santiago. This work was also supported by a Framework Partnership Agreement between the Consellería de Sanidad de la Xunta de Galicia and GENVIP-IDIS- 2021–2024 (SERGAS-IDIS March 2021; Spain). In addition, it received support from (i) ISCIII: PI24/00757 (to N.M.); TRINEO: PI22/00162; DIAVIR: DTS19/00049; Resvi-Omics: PI19/01039 (to A.S.), ReSVinext: PI16/01569, Enterogen: PI19/01090, OMI-COVI-VAC: PI22/00406 (to F.M.-T.), cofnanciados FEDER, (ii) GAIN: IN607B 2020/08 and IN607 A 2023/02 (to A.S.), GEN-COVID (IN845D 2020/23 (to F.M.-T.), IIN607 A2021/05 (to F.M.-T.); (iii) ACIS: BI-BACVIR (PRIS- 3, to A.S.), CovidPhy (SA 304 C, to A.S.), PneumoTrack (PRIST-VAL, to A.S.), and Respisal (PRIST-VAL, to F.M.-T.); and (iv) Consorcio Centro de Investigación Biomédica en Red de Enfermedades Respiratorias (CB21/06/00103; to A.S. and F.M.-T.). This study was also supported by grants from the Galician Supercomputing Center (CESGA), the Spanish Ministry of Science and Innovation, the Galician Government, and the European Regional Development Fund (ERDF), the European Seventh Framework Programme for Research and Technological Development (FP7) under the EUCLIDS project (grant agreement number 279185). The funders did not have any role in study design, data collection, analysis, interpretation, manuscript design and writing, or decision to submit the manuscript for publication. All authors approved the manuscript and are counted as responsible for its content. DS Minerva RD 29 abr 2026