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

Hulme, WJORCID logo; Williamson, EJORCID logo; Green, ACORCID logo; Bhaskaran, KORCID logo; McDonald, HIORCID logo; Rentsch, CTORCID logo; Schultze, AORCID logo; Tazare, JORCID logo; Curtis, HJORCID logo; Walker, AJORCID logo; +32 more...Tomlinson, LAORCID logo; Palmer, TORCID logo; Horne, EMORCID logo; MacKenna, BORCID logo; Morton, CEORCID logo; Mehrkar, AORCID logo; Morley, JORCID logo; Fisher, LORCID logo; Bacon, SCORCID logo; Evans, DORCID logo; Inglesby, PORCID logo; Hickman, GORCID logo; Davy, SORCID logo; Ward, T; Croker, RORCID logo; Eggo, RMORCID logo; Wong, AYORCID logo; Mathur, RORCID logo; Wing, KORCID logo; Forbes, HORCID logo; Grint, DJORCID logo; Douglas, IJORCID logo; Evans, SJORCID logo; Smeeth, LORCID logo; Bates, CORCID logo; Cockburn, JORCID logo; Parry, J; Hester, F; Harper, S; Sterne, JAORCID logo; Hernán, MAORCID logo; Goldacre, BORCID logo and (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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