Effectiveness of the Pfizer-BioNTech and Oxford-AstraZeneca vaccines on covid-19 related symptoms, hospital admissions, and mortality in older adults in England: test negative case-control study
Study (n=156 930 aged ≥70 years) found single dose of either BNT162b2 or ChAdOx1-S provides significant protection against covid-19 and further protection against severe disease lasting ≥ 6 weeks, including against UK variant of concern (B.1.1.7)
Source:
British Medical Journal
SPS commentary:
With BNT162b2, vaccine effectiveness reached 61% from 28 to 34 days after vaccination, then plateaued. With ChAdOx1-S, effects were seen from 14 to 20 days after vaccination, reaching an effectiveness of 60% from 28 to 34 days, increasing to 73% from day 35 onwards. On top of the protection against symptomatic disease, a further 43% reduced risk of emergency hospital admission and 51% reduced risk of death was observed in those who had received one dose of BNT162b2. Participants who had received one dose of ChAdOx1-S had a further 37% reduced risk of emergency hospital admission.
According to an editorial, these findings strongly support a protective effect among older adults during the initial stages of the UK’s first covid-19 vaccination programme. It stresses however, that both vaccine types remain vaccine candidates that are still being evaluated for effectiveness and safety during ongoing confirmatory phase IV trials.