Volunteer Thabisle Khlatshwayo, who received her first shot for a COVID-19 vaccine trial, is tested before receiving her second shot at a vaccine trial facility set at Soweto's Chris Sani Baragwanath Hospital outside Johannesburg, South Africa, Monday Nov. 30, 2020. Over 2000 South African volunteers are on AstraZeneca's experimental coronavirus vaccine trial. (AP Photo/Jerome Delay)

Volunteer Thabisle Khlatshwayo, who received her first shot for a COVID-19 vaccine trial, receives her second shot at a vaccine trial facility set at Soweto's Chris Sani Baragwanath Hospital outside Johannesburg, South Africa, Monday Nov. 30, 2020. Over 2000 South African volunteers are on AstraZeneca's experimental coronavirus vaccine trial. (AP Photo/Jerome Delay)