{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,18]],"date-time":"2026-03-18T01:33:29Z","timestamp":1773797609283,"version":"3.50.1"},"reference-count":20,"publisher":"BMJ","issue":"7","license":[{"start":{"date-parts":[[2022,7,18]],"date-time":"2022-07-18T00:00:00Z","timestamp":1658102400000},"content-version":"unspecified","delay-in-days":17,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100025092","name":"Ontario Ministry of Health","doi-asserted-by":"crossref","award":["No grant number was assigned to the funding award"],"award-info":[{"award-number":["No grant number was assigned to the funding award"]}],"id":[{"id":"10.13039\/501100025092","id-type":"DOI","asserted-by":"crossref"}]},{"name":"Ontario Academic Health Sciences Centre AFP Innovation Fund","award":["No grant number was assigned to the funding award"],"award-info":[{"award-number":["No grant number was assigned to the funding award"]}]}],"content-domain":{"domain":["bmj.com"],"crossmark-restriction":true},"short-container-title":["BMJ Open"],"accepted":{"date-parts":[[2022,6,30]]},"published-print":{"date-parts":[[2022,7]]},"abstract":"<jats:sec>\n                    <jats:title>Objective<\/jats:title>\n                    <jats:p>To compare outcomes between O and non-O blood groups, and by modified RNA (mRNA) and adenovirus-vectored (Ad-V) vaccines.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Design<\/jats:title>\n                    <jats:p>Population-based cohort study.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Setting<\/jats:title>\n                    <jats:p>All of Ontario, Canada. Linked data sets captured clinical encounters, vaccinations and laboratory testing for SARS-CoV-2.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Participants<\/jats:title>\n                    <jats:p>Individuals aged 12+ years with known ABO blood group and free of SARS-CoV-2 before 15 January 2021.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Main outcomes measures<\/jats:title>\n                    <jats:p>The main exposure, first SARS-CoV-2 vaccination, was modelled in a time-varying manner. O and non-O blood group was known prior to vaccination. SARS-CoV-2 infection, and severe COVID-19 (hospitalisation or death), were assessed starting 14 days after vaccination, up to 27 June 2021.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>2 472 261 individuals were included. 1 743 916 (70.5%) had at least one vaccination, of which 24.6% were fully vaccinated. Those vaccinated were more likely to be women, older in age, residing in a higher-income area and have higher rates of certain comorbid conditions, like cancer, diabetes and hypertension. Relative to unvaccinated, after receiving their first mRNA (adjusted HR (aHR) 0.46, 95% CI 0.44 to 0.47) or Ad-V (aHR 0.49, 95% CI 0.44 to 0.54) vaccine, the risk of SARS-CoV-2 infection was lower, as was severe COVID-19 (aHR 0.29, 95% CI 0.20 to 0.43 (mRNA); aHR 0.29, 95% CI 0.26 to 0.33 (Ad-V)). Stratifying by blood group produced similar results. For example, after first mRNA vaccination, the aHR of severe COVID-19 was 0.31 (95% CI 0.27 to 0.36) among non-O blood groups, and 0.27 (95% CI 0.22 to 0.32) among O blood groups, relative to unvaccinated. Fully vaccinated individuals had the lowest risk of SARS-CoV-2 and severe COVID-19.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>SARS-CoV-2 infection and severe COVID-19 are reduced by vaccination. This effect does not vary by vaccine type or blood group, but is more pronounced among fully, than partially, vaccinated individuals.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1136\/bmjopen-2021-059944","type":"journal-article","created":{"date-parts":[[2022,7,18]],"date-time":"2022-07-18T11:55:51Z","timestamp":1658145351000},"page":"e059944","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":7,"title":["SARS-CoV-2 vaccination, ABO blood group and risk of COVID-19: population-based cohort study"],"prefix":"10.1136","volume":"12","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-1635-4658","authenticated-orcid":false,"given":"Joel G","family":"Ray","sequence":"first","affiliation":[{"name":"Medicine, St. Michael's Hospital, Toronto, Ontario, Canada"},{"name":"ICES, Toronto, Ontario, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Alison L","family":"Park","sequence":"additional","affiliation":[{"name":"ICES, Toronto, Ontario, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"239","published-online":{"date-parts":[[2022,7,18]]},"reference":[{"key":"2025121401213524000_12.7.e059944.1","doi-asserted-by":"publisher","DOI":"10.1056\/NEJMoa2034577"},{"key":"2025121401213524000_12.7.e059944.2","doi-asserted-by":"crossref","first-page":"1824","DOI":"10.1056\/NEJMoa2034201","article-title":"Interim results of a phase 1-2a trial of Ad26.COV2.S Covid-19 vaccine","volume":"384","author":"Sadoff","year":"2021","journal-title":"N Engl J Med"},{"key":"2025121401213524000_12.7.e059944.3","doi-asserted-by":"crossref","DOI":"10.3390\/vaccines9050467","article-title":"Efficacy and safety of COVID-19 vaccines: a systematic review and meta-analysis of randomized clinical trials","volume":"9","author":"Pormohammad","year":"2021","journal-title":"Vaccines"},{"key":"2025121401213524000_12.7.e059944.4","doi-asserted-by":"publisher","DOI":"10.1056\/NEJMoa2035389"},{"key":"2025121401213524000_12.7.e059944.5","doi-asserted-by":"publisher","DOI":"10.15585\/MMWR.MM7013E3"},{"key":"2025121401213524000_12.7.e059944.6","doi-asserted-by":"crossref","unstructured":"Ray JG , Schull MJ , Vermeulen MJ , et al . Association Between ABO and Rh Blood Groups and SARS-CoV-2 Infection or Severe COVID-19 Illness : A Population-Based Cohort Study. Ann Intern Med 2020:M20\u20134511.","DOI":"10.7326\/M20-4511"},{"key":"2025121401213524000_12.7.e059944.7","doi-asserted-by":"crossref","first-page":"849","DOI":"10.1111\/vox.13076","article-title":"ABO blood group and COVID-19: a review on behalf of the ISBT COVID-19 Working group","volume":"116","author":"Goel","year":"2021","journal-title":"Vox Sang"},{"key":"2025121401213524000_12.7.e059944.8","unstructured":"ICES . ICES COVID-19 Dashboard, 2022. Available: https:\/\/www.ices.on.ca\/DAS\/AHRQ\/COVID-19-Dashboard#vaccinecoverage [Accessed 16 May 2022]."},{"key":"2025121401213524000_12.7.e059944.9","unstructured":"Ontario Ministry of Health . COVID-19 vaccine data in Ontario, 2022. Available: https:\/\/data.ontario.ca\/dataset\/covid-19-vaccine-data-in-ontario [Accessed 16 May 2022]."},{"key":"2025121401213524000_12.7.e059944.10","doi-asserted-by":"publisher","DOI":"10.1136\/bmj.n1943"},{"key":"2025121401213524000_12.7.e059944.11","doi-asserted-by":"publisher","DOI":"10.1093\/aje\/kwm324"},{"key":"2025121401213524000_12.7.e059944.12","unstructured":"National Advisory Committee on immunization (NACI): statements and publications. recommendations on the use of COVID-19 vaccines, 2021. Available: https:\/\/www.canada.ca\/en\/public-health\/services\/immunization\/national-advisory-committee-on-immunization-naci\/recommendations-use-covid-19-vaccines.html#t19 [Accessed 15 Aug 2021]."},{"key":"2025121401213524000_12.7.e059944.13","doi-asserted-by":"publisher","DOI":"10.1016\/J.Blre.2020.100785"},{"key":"2025121401213524000_12.7.e059944.14","doi-asserted-by":"publisher","DOI":"10.1136\/jmg.2.2.122"},{"key":"2025121401213524000_12.7.e059944.15","doi-asserted-by":"crossref","first-page":"21","DOI":"10.1017\/S0022172400053365","article-title":"The effect of ABO blood groups on the incidence of epidemic influenza and on the response to live attenuated and detergent split influenza virus vaccines","volume":"80","author":"Mackenzie","year":"1978","journal-title":"J Hyg"},{"key":"2025121401213524000_12.7.e059944.16","doi-asserted-by":"crossref","first-page":"412","DOI":"10.1007\/s00508-005-0366-3","article-title":"Lack of impact of ABO blood group or corresponding isoantibodies on the immune response after rabies vaccination","volume":"117","author":"Buchta","year":"2005","journal-title":"Wien Klin Wochenschr"},{"key":"2025121401213524000_12.7.e059944.17","doi-asserted-by":"publisher","DOI":"10.1128\/CVI.00123-10"},{"key":"2025121401213524000_12.7.e059944.18","doi-asserted-by":"publisher","DOI":"10.1056\/NEJMoa2107715"},{"key":"2025121401213524000_12.7.e059944.19","doi-asserted-by":"crossref","DOI":"10.1001\/jamaoncol.2021.1715","article-title":"Time-Related biases in nonrandomized COVID-19-Era studies using real-world data","author":"Calip","year":"2021","journal-title":"JAMA Oncol"},{"key":"2025121401213524000_12.7.e059944.20","doi-asserted-by":"crossref","first-page":"1431","DOI":"10.1056\/NEJMe2113151","article-title":"Covid-19 vaccine effectiveness and the test-negative design","volume":"385","author":"Dean","year":"2021","journal-title":"N Engl J Med Overseas Ed"}],"container-title":["BMJ Open"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/syndication.highwire.org\/content\/doi\/10.1136\/bmjopen-2021-059944","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,12,14]],"date-time":"2025-12-14T09:21:43Z","timestamp":1765704103000},"score":1,"resource":{"primary":{"URL":"https:\/\/bmjopen.bmj.com\/lookup\/doi\/10.1136\/bmjopen-2021-059944"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2022,7]]},"references-count":20,"journal-issue":{"issue":"7","published-online":{"date-parts":[[2022,7,18]]},"published-print":{"date-parts":[[2022,7]]}},"alternative-id":["10.1136\/bmjopen-2021-059944"],"URL":"https:\/\/doi.org\/10.1136\/bmjopen-2021-059944","relation":{},"ISSN":["2044-6055","2044-6055"],"issn-type":[{"value":"2044-6055","type":"print"},{"value":"2044-6055","type":"electronic"}],"subject":[],"published":{"date-parts":[[2022,7]]}}}