The AstraZeneca vaccine ran into trouble in South Africa.
Preliminary findings, which have not yet been peer-reviewed, of a study of around 2,000 participants (median age 31), were disappointing. The vaccine had been showing a 75% efficacy against mild to moderate COVID cases, before the B.1.351 strain became dominant in South Africa. These days, 90% of new infections in SA are of the new strain. For these new infections, the efficacy seems to have dropped to just 22% percent, based on 42 symptomatic cases. The 42 cases is too small a number to draw firm conclusions, but it’s a big red flag, for sure.
South African health authorities have now put the roll-out of the AstraZeneca vaccine on hold. They are negotiating with Johnson & Johnson for 20 million doses, and trying to ascertain if there is value in giving shots of the AstraZeneca vaccine to younger people.