{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,27]],"date-time":"2026-02-27T17:51:28Z","timestamp":1772214688856,"version":"3.50.1"},"reference-count":31,"publisher":"Public Library of Science (PLoS)","issue":"9","license":[{"start":{"date-parts":[[2022,9,13]],"date-time":"2022-09-13T00:00:00Z","timestamp":1663027200000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["www.plosone.org"],"crossmark-restriction":false},"short-container-title":["PLoS ONE"],"abstract":"<jats:sec id=\"sec001\">\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>Using data from electronic health registries, this study intended to estimate the COVID-19 vaccine effectiveness (VE) in the population aged 65 years and more, against symptomatic infection, COVID-19-related hospitalizations, and deaths, overall and by time since complete vaccination for the period February to September 2021<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"sec002\">\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>We established a cohort of individuals aged 65 and more years old, resident in Portugal mainland, using the National Health Service User number to link eight electronic health registries. Outcomes included were symptomatic SARS-CoV-2 infections, COVID-19-related hospitalizations or deaths. The exposures of interest were the mRNA vaccines (Comirnaty or Spikevax) and the viral vector (Vaxzevria) vaccine. Complete schedule VE was estimated as one minus the confounder adjusted hazard ratio, for each outcome, estimated by time-dependent Cox regression with time-dependent vaccine exposure.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"sec003\">\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>For the cohort of individuals aged 65\u201379 years, complete scheme VE against symptomatic infection varied 43 (95%CI: 37\u201349) (Vaxzevria) and 65 (95%CI: 62\u201368) (mRNA vaccines). This estimate was slightly lower in the \u226580 years cohort (53, 95%CI: 45\u201360) for mRNA vaccines). VE against COVID-19 hospitalization varied between 89% (95%CI: 52\u201394) for Vaxzevria and 95% (95%CI: 93\u201397) for mRNA vaccines for the cohort aged 65\u201379 years and was 76% (95%CI: 67\u201383) for mRNA vaccines in the \u226580 years cohort. High VE against COVID-19-related deaths was estimated, for both vaccine types, 95% and 81 (95%CI:76\u201386) for the 65\u201379 years and the \u226580 years cohort, respectively. We observed a significant waning of VE against symptomatic infection, with VE estimates reaching approximately 34% for both vaccine types and cohorts. Significant waning was observed for the COVID-19 hospitalizations in the \u226580 years cohort (decay from 83% (95%CI:68 to 91) 14\u201341 days to 63% (95%CI:37 to 78) 124 days after mRNA second dose). No significant waning effect was observed for COVID-19-related deaths in the period of follow-up of either cohort.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"sec004\">\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>In a population with a high risk of SARS-CoV-2 complications, we observed higher overall VE estimates against more severe outcomes for both age cohorts when compared to symptomatic infections. Considering the analysis of VE according to time since complete vaccination, the results showed a waning effect for both age cohorts in symptomatic infection and COVID-19 hospitalization for the 80 and more years cohort.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1371\/journal.pone.0274008","type":"journal-article","created":{"date-parts":[[2022,9,13]],"date-time":"2022-09-13T13:30:30Z","timestamp":1663075830000},"page":"e0274008","update-policy":"https:\/\/doi.org\/10.1371\/journal.pone.corrections_policy","source":"Crossref","is-referenced-by-count":15,"title":["COVID-19 vaccine effectiveness against symptomatic SARS-CoV-2 infections, COVID-19 related hospitalizations and deaths, among individuals aged \u226565 years in Portugal: A cohort study based on data-linkage of national registries February-September 2021"],"prefix":"10.1371","volume":"17","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-1849-1499","authenticated-orcid":true,"given":"Ausenda","family":"Machado","sequence":"first","affiliation":[]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5772-2416","authenticated-orcid":true,"given":"Irina","family":"Kislaya","sequence":"additional","affiliation":[]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2264-4723","authenticated-orcid":true,"given":"Ana Paula","family":"Rodrigues","sequence":"additional","affiliation":[]},{"given":"Duarte","family":"Sequeira","sequence":"additional","affiliation":[]},{"given":"Jo\u00e3o","family":"Lima","sequence":"additional","affiliation":[]},{"given":"Camila","family":"Cruz","sequence":"additional","affiliation":[]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5939-2577","authenticated-orcid":true,"given":"Pedro Pinto","family":"Leite","sequence":"additional","affiliation":[]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0206-5874","authenticated-orcid":true,"given":"Carlos","family":"Matias Dias","sequence":"additional","affiliation":[]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6230-7209","authenticated-orcid":true,"given":"Baltazar","family":"Nunes","sequence":"additional","affiliation":[]}],"member":"340","published-online":{"date-parts":[[2022,9,13]]},"reference":[{"key":"pone.0274008.ref001","volume-title":"Plano de Vacina\u00e7\u00e3o contra a COVID-19","author":"Minist\u00e9rio da Sa\u00fade","year":"2020"},{"key":"pone.0274008.ref002","author":"INFARMED","year":"2020","journal-title":"Vacinas aprovadas (quadro-resumo)"},{"key":"pone.0274008.ref003","article-title":"Norma 003\/2021","author":"Dire\u00e7\u00e3o Geral de Sa\u00fade","year":"2021","journal-title":"Campanha de Vacina\u00e7\u00e3o contra a COVID-19 Vacina VAXZEVRIA. 08\/02\/2021"},{"key":"pone.0274008.ref004","volume-title":"Campanha de Vacina\u00e7\u00e3o contra a COVID-19 Vacina VAXZEVRIA. 08\/02\/2021. 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