Comparative effectiveness of ChAdOx1 versus BNT162b2 covid-19 vaccines in health and social care workers in England: cohort study using OpenSAFELY.

William J Hulme ORCID logo; Elizabeth J Williamson ORCID logo; Amelia CA Green ORCID logo; Krishnan Bhaskaran ORCID logo; Helen I McDonald ORCID logo; Christopher T Rentsch ORCID logo; Anna Schultze ORCID logo; John Tazare ORCID logo; Helen J Curtis ORCID logo; Alex J Walker ORCID logo; +32 more... Laurie A Tomlinson ORCID logo; Tom Palmer ORCID logo; Elsie MF Horne ORCID logo; Brian MacKenna ORCID logo; Caroline E Morton ORCID logo; Amir Mehrkar ORCID logo; Jessica Morley ORCID logo; Louis Fisher ORCID logo; Sebastian CJ Bacon ORCID logo; David Evans ORCID logo; Peter Inglesby ORCID logo; George Hickman ORCID logo; Simon Davy ORCID logo; Tom Ward; Richard Croker ORCID logo; Rosalind M Eggo ORCID logo; Angel YS Wong ORCID logo; Rohini Mathur ORCID logo; Kevin Wing ORCID logo; Harriet Forbes ORCID logo; Daniel J Grint ORCID logo; Ian J Douglas ORCID logo; Stephen JW Evans ORCID logo; Liam Smeeth ORCID logo; Chris Bates ORCID logo; Jonathan Cockburn ORCID logo; John Parry; Frank Hester; Sam Harper; Jonathan AC Sterne ORCID logo; Miguel A Hernán ORCID logo; Ben Goldacre ORCID logo; (2022) Comparative effectiveness of ChAdOx1 versus BNT162b2 covid-19 vaccines in health and social care workers in England: cohort study using OpenSAFELY. BMJ, 378. e068946-. DOI: 10.1136/bmj-2021-068946
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OBJECTIVE: To compare the effectiveness of the BNT162b2 mRNA (Pfizer-BioNTech) and the ChAdOx1 (Oxford-AstraZeneca) covid-19 vaccines against infection and covid-19 disease in health and social care workers. DESIGN: Cohort study, emulating a comparative effectiveness trial, on behalf of NHS England. SETTING: Linked primary care, hospital, and covid-19 surveillance records available within the OpenSAFELY-TPP research platform, covering a period when the SARS-CoV-2 Alpha variant was dominant. PARTICIPANTS: 317 341 health and social care workers vaccinated between 4 January and 28 February 2021, registered with a general practice using the TPP SystmOne clinical information system in England, and not clinically extremely vulnerable. INTERVENTIONS: Vaccination with either BNT162b2 or ChAdOx1 administered as part of the national covid-19 vaccine roll-out. MAIN OUTCOME MEASURES: Recorded SARS-CoV-2 positive test, or covid-19 related attendance at an accident and emergency (A&E) department or hospital admission occurring within 20 weeks of receipt of the first vaccine dose. RESULTS: Over the duration of 118 771 person-years of follow-up there were 6962 positive SARS-CoV-2 tests, 282 covid-19 related A&E attendances, and 166 covid-19 related hospital admissions. The cumulative incidence of each outcome was similar for both vaccines during the first 20 weeks after vaccination. The cumulative incidence of recorded SARS-CoV-2 infection 20 weeks after first-dose vaccination with BNT162b2 was 21.7 per 1000 people (95% confidence interval 20.9 to 22.4) and with ChAdOx1 was 23.7 (21.8 to 25.6), representing a difference of 2.04 per 1000 people (0.04 to 4.04). The difference in the cumulative incidence per 1000 people of covid-19 related A&E attendance at 20 weeks was 0.06 per 1000 people (95% CI -0.31 to 0.43). For covid-19 related hospital admission, this difference was 0.11 per 1000 people (-0.22 to 0.44). CONCLUSIONS: In this cohort of healthcare workers where we would not anticipate vaccine type to be related to health status, we found no substantial differences in the incidence of SARS-CoV-2 infection or covid-19 disease up to 20 weeks after vaccination. Incidence dropped sharply at 3-4 weeks after vaccination, and there were few covid-19 related hospital attendance and admission events after this period. This is in line with expected onset of vaccine induced immunity and suggests strong protection against Alpha variant covid-19 disease for both vaccines in this relatively young and healthy population of healthcare workers.


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