{"doi":"10.1093/ofid/ofae547","title":"Effectiveness of the First and Second Severe Acute Respiratory Syndrome Coronavirus 2 Vaccine Dose: A Nationwide Cohort Study From Austria on Hybrid Versus Natural Immunity","abstract":"<h4>Background</h4>We aimed to evaluate the effectiveness of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccinations in previously SARS-CoV-2-infected adults in the general population of Austria during the Delta wave and with extended follow-up.<h4>Methods</h4>In a nationwide retrospective cohort study, we calculated age-, sex-, and nursing home residency-adjusted Cox proportional hazard ratios (HRs) of coronavirus disease 2019 (COVID-19) deaths, SARS-CoV-2 infections, and non-COVID-19 deaths from 1 October to 31 December 2021, and secondarily with extended follow-up to 30 June 2022. Relative vaccine effectiveness (rVE) is rVE = (1 - HR) × 100.<h4>Results</h4>Among 494 646 previously infected adults, 169 543 had received 2 vaccine doses, 133 567 had received 1 dose, and 190 275 were unvaccinated at baseline. We recorded 17 COVID-19 deaths (6 vaccinated, 11 unvaccinated) and 8209 SARS-CoV-2 infections. Absolute risk of COVID-19 deaths was 0.003%. rVE estimates for COVID-19 deaths and reinfections exceeded 75% until the end of 2021 but decreased substantially with extended follow-up. The risk of non-COVID-19 death was lower in those vaccinated versus unvaccinated.<h4>Conclusions</h4>First and second SARS-CoV-2 vaccine doses appear effective in the short-term, but with diminishing effectiveness over time. The extremely low COVID-19 mortality, regardless of vaccination, indicates strong protection of previous infection against COVID-19 death. Lower non-COVID-19 mortality in the vaccinated population might suggest a healthy vaccinee bias.","journal":"Open Forum Infectious Diseases","year":2024,"id":9250,"datarank":0.32958368660043297,"base_score":2.1972245773362196,"endowment":2.1972245773362196,"self_citation_contribution":0.32958368660043297,"citation_network_contribution":0.0,"self_endowment_contribution":0.32958368660043297,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":8,"citer_count":2,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.1701,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2024-09-19","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":14474,"name":"Uwe Riedmann","orcid":"0000-0002-2541-9604","position":1,"is_corresponding":false},{"id":17138,"name":"Lukas Richter","orcid":"0000-0001-6982-6239","position":2,"is_corresponding":false},{"id":69425,"name":"Ali Chakeri","orcid":"0009-0005-7793-5271","position":3,"is_corresponding":false},{"id":61126,"name":"Ziad El-Khatib","orcid":null,"position":4,"is_corresponding":false},{"id":17139,"name":"Martin Sprenger","orcid":"0000-0002-7232-6515","position":5,"is_corresponding":false},{"id":3315,"name":"Christian Trummer","orcid":"0000-0001-5817-4554","position":7,"is_corresponding":false},{"id":17140,"name":"Peter Willeit","orcid":"0000-0002-1866-7159","position":8,"is_corresponding":false},{"id":54429,"name":"Harald Schennach","orcid":null,"position":9,"is_corresponding":false},{"id":54430,"name":"Bernhard Benka","orcid":"0000-0002-0913-8677","position":10,"is_corresponding":false},{"id":42714,"name":"Dirk Werber","orcid":"0000-0002-8076-788X","position":11,"is_corresponding":false},{"id":17141,"name":"Tracy  Beth Høeg","orcid":"0000-0002-2341-6573","position":12,"is_corresponding":false},{"id":148,"name":"John P. A. Ioannidis","orcid":"0000-0003-3118-6859","position":13,"is_corresponding":false},{"id":3313,"name":"Stefan Pilz","orcid":"0000-0002-7959-1311","position":14,"is_corresponding":false},{"id":17142,"name":"Lukáš Richter","orcid":"0000-0002-3304-3491","position":15,"is_corresponding":false},{"id":61465,"name":"Ziad El‐Khatib","orcid":null,"position":16,"is_corresponding":false},{"id":3317,"name":"Verena Theiler‐Schwetz","orcid":"0000-0002-2378-689X","position":17,"is_corresponding":false},{"id":17137,"name":"Alena Chalupka","orcid":"0009-0000-3291-1456","position":0,"is_corresponding":true}],"reference_count":31,"raw_metadata":{"citation_network_status":"fetched"},"created_at":"2026-03-01T18:20:47.508186Z","pmid":null,"pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}