Humphreys, JamesBlake, AlexandreNicolay, NathalieBraeye, ToonVan Evercooren, IzaakHansen, Christian HolmMoustsen-Helms, Ida RaskSacco, ChiaraMateo-Urdiales, AlbertoCastilla, JesúsMartínez-Baz, IvánMachado, AusendaBrito, AndréLjung, RickardPihlstrom, NicklasMansiaux, YohannMonge, SusanaBacci, SabrinaNunes, BaltazarVEBIS-Lot 4 working group2026-01-292026-01-292025-10-03Vaccine. 2025 Oct 3:64:127752. doi: 10.1016/j.vaccine.2025.127752. Epub 2025 Sep 190264-410Xhttp://hdl.handle.net/10400.18/10784VEBIS-Lot 4 working group: Joris Van Loenhout, Massimo Fabiani, Patricia Soares, Anthony Nardone, Esther Kissling.We estimated vaccine effectiveness (VE) of Omicron JN.1-adapted COVID-19 vaccines administered during the 2024 autumnal vaccination campaign against COVID-19 hospitalisation and death among eligible individuals aged ≥65 years. The study period was October 2024-January 2025. Using a common protocol across six EU/EEA study sites, we linked electronic health records to construct retrospective cohorts and applied Cox modelling to estimate VE via confounder-adjusted hazard ratios. The majority of vaccines administered during the study period were Omicron JN.1-adapted COVID-19 vaccines (99 %). VE against hospitalisation was 60 % (95 % Confidence Interval: 48-70 %) and against COVID-19-related death was 78 % (95 %CI: 64-87 %) among individuals aged 65-79 years; 58 % (95 %CI: 48-66 %) and 62 % (95 %CI: 32-79 %) among those aged ≥80 years. These results indicate high effectiveness in the initial months of the campaign. Continued monitoring is necessary to confirm these results, including estimates of VE in those with longer time since vaccination and during different variant predominance periods.engCOVID-19Cohort DesignElectronic Health RecordsHospitalisationMulti-country StudySARS-CoV-2Vaccine EffectivenessVEBIS-Lot 4EuropeCuidados de SaúdeInfecções Respiratóriasjournal article10.1016/j.vaccine.2025.12775240974735