South Africa received one million AstraZeneca doses last week and had hoped to start vaccinating health workers soon but results that are yet to be peer-reviewed show minimal protection against mild or moderate infection from the B.1.351 variant.
The experimental drug, developed by the US National Institutes of Health and Moderna, will be tried on 30,000 volunteers in the US who won't know if they're getting the real shot or a placebo in order to see which group experiences more infections.