August 18. The Oxford-AstraZeneca jab, though initially less effective, offers the same high protection as the Pfizer-BioNTech after four to five months, the largest study of its kind suggests. But neither is as effective as it is against the Alpha variant.
There is insufficient data for Moderna. But researchers believe it “almost certainly at least as good as the others”.
They analyzed two and a half million tests results from 743,526 participants in the UK’s Covid-19 household-infection survey – led by Oxford University and the Office for National Statistics.
The Pfizer-BioNTech vaccine had 93% effectiveness against symptomatic infection two weeks after the second dose, compared with Oxford-AstraZeneca’s 71%.
Over time, however, the Pfizer-BioNTech’s effectiveness dropped while the Oxford-AstraZeneca’s remained largely the same.