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Project #62:
Comparing effectiveness of the Pfizer-BioNTech vaccine with the Oxford-AstraZeneca vaccine in Health and Social Care workers in England


Many studies have been conducted that estimate the effect of COVID-19 vaccines in reducing infection or disease compared with unvaccinated people. However, there have been no randomised controlled trials that have made direct head-to-head comparisons. Such comparisons are difficult in observational data without the rollout of both vaccines across the same population at the same time. The concurrent rollout of the Pfizer-BioNTech vaccine and the Oxford-AstraZeneca vaccine in health and social care workers in England provides a rare opportunity to do this.

We compared effectiveness in around ⅓ million health and social care workers in England, vaccinated between 4 January and 28 February 2021, and followed up for 20 weeks. Primary outcomes were recorded SARS-CoV-2 infection, COVID-19-related accident and emergency attendance, and COVID-19-related hospital admission.

We found very little difference in between the vaccines on the studied outcomes. Whilst some material differences in the protective effect may exist, both are extremely effective for reducing COVID-19 disease and there were too few events to reliably detect such differences up to 20 weeks after vaccination.


  • Study leads: William Hulme
  • Organisation: University of Oxford and London School of Hygiene and Tropical Medicine