Impact of prior SARS-COV-2 infection and vaccination on COVID-19 hospital admission and mortality amongst nursing home residents.

"Declarations Conflict of interestThe author(s) declare that they have no conflict of interest. Statement of human and animal rightsThe study protocol was approved by the Ethics Committee of the Basque Country (reference PI2020123). Informed consentThe Basque Country Ethics Committee (PI2020123) approved the waiver of informed consent in this study due to the pandemic exceptional conditions and retrospective design. RegistrationClinicalTrials.gov Identifier: NCT04463706. Conflict of interest The author(s) declare that they have no conflict of interest."

"Funding This work was supported in part by the health outcomes group from Galdakao-Barrualde Health Organization; the Kronikgune Institute for Health Service Research and Biocruces Bizkaia Health Research Institute; and the thematic networks–REDISSEC (Red de Investigación en Servicios de Salud en Enfermedades Crónicas RD16/0001/0018) and Network for Research on Chronicity, Primary Care, and Health Promotion (RICAPPS) –of the Instituto de Salud Carlos III."

"Trial registration ClinicalTrials.gov Identifier: NCT04463706."