Sentís, AlexisKislaya, IrinaNicolay, NathalieMeijerink, HintaStarrfelt, JosteinMartínez-Baz, IvánCastilla Catalán, JesúsNielsen, Katrine FinderupHansen, Christian HolmEmborg, Hanne-DortheNardone, AnthonyDerrough, TarikValenciano, MartaNunes, BaltazarMonge, SusanaVEBIS-Lot4 working groupLarrauri, AmparoMazagatos, Clara2023-02-072023-02-072022-07Euro Surveill. 2022 Jul;27(30):2200551.http://hdl.handle.net/20.500.12105/15461By employing a common protocol and data from electronic health registries in Denmark, Navarre (Spain), Norway and Portugal, we estimated vaccine effectiveness (VE) against hospitalisation due to COVID-19 in individuals aged ≥ 65 years old, without previous documented infection, between October 2021 and March 2022. VE was higher in 65-79-year-olds compared with ≥ 80-year-olds and in those who received a booster compared with those who were primary vaccinated. VE remained high (ca 80%) between ≥ 12 and < 24 weeks after the first booster administration, and after Omicron became dominant.engVoRhttp://creativecommons.org/licenses/by/4.0/COVID-19Delta variantOmicron variantVaccination booster doseVaccination primary courseVaccine effectivenessCOVID-19COVID-19 VaccinesAgedElectronicsHospitalizationHumansPilot ProjectsRegistriesVaccine EfficacyEstimation of COVID-19 vaccine effectiveness against hospitalisation in individuals aged ≥ 65 years using electronic health registries; a pilot study in four EU/EEA countries, October 2021 to March 2022Atribución 4.0 Internacional359040592730220055110.2807/1560-7917.ES.2022.27.30.22005511560-7917Euro surveillance : bulletin Europeen sur les maladies transmissibles = European communicable disease bulletinopen access