2026-05-17T14:54:04Zhttps://repisalud.isciii.es/rest/oai/request

oai:repisalud.isciii.es:20.500.12105/273282026-04-07T09:38:41Zcom_20.500.12105_2052com_20.500.12105_2051col_20.500.12105_19608col_20.500.12105_19613

00925njm 22002777a 4500 dc Campos Mena, Sandra author Pérez-Gimeno, Gloria author Lorusso, Nicola author Álvarez Río, Virginia author Basile, Luca author Batalla Rebollo, Noa author García-Comas, Luis author Andreu Ivorra, Blanca author Pérez-Panadés, Jordi author Ramos Marín, Violeta author Castrillejo, Daniel author Fernández Ibáñez, Ana author Rafael de la Cruz López, María Ángeles author Nuñez, Olivier author Monge Corella, Susana author Grupo SiVIRA de vigilancia y efectividad vacunal en España author 2025-12-09 Effectiveness of nirsevimab against respiratory syncytial virus (RSV) hospitalization during the 2024/2025 season in Spain was estimated using a test-negative design (TND) and hospital-based respiratory infections surveillance data. Children born between 1 April 2024 and 31 March 2025 and hospitalized with severe respiratory infection between the start of the 2024 immunization campaign (regionally variable, between 16 September and 1 October 2024) and 31 March 2025 were systematically RT-PCR RSV-tested within 10 days of symptom onset and classified as cases if positive or controls if negative. Nirsevimab effectiveness ((1 - odds ratio) × 100) was estimated using logistic regression, adjusted for admission week, age, sex, high-risk factors, and regional RSV hospitalization rate. We included 199 cases (68.8% immunized) and 360 controls (86.4% immunized). Overall effectiveness was 65.5% (95% confidence interval: 45.2 to 78.3). Effectiveness was similar among infants born before and after the campaign start (63.6% vs. 70.4%, respectively). We found an unexpected early decrease in effectiveness with increasing time since immunization and age, albeit with wide confidence intervals for some groups. Strong age-period-cohort effects and potential sources of bias were identified, highlighting the need to further explore methodological challenges of implementing the TND in the dynamic population of newborns. Campos Mena S, Pérez-Gimeno G, Lorusso N, et al. Monitoring effectiveness of nirsevimab immunization against RSV hospitalization using surveillance data: a test-negative case–control study, Spain, October 2024–March 2025. Epidemiology and Infection. 2026;154:e5. doi:10.1017/S0950268825100782. 10.1017/S0950268825100782 Epidemiology & Infection 41362152 https://hdl.handle.net/20.500.12105/27328 Immunization Infant Nirsevimab Respiratory syncytial virus Surveillance system Test-negative design Monitoring effectiveness of nirsevimab immunization against RSV hospitalization using surveillance data: a test-negative case-control study, Spain, October 2024-March 2025.