A medical worker administers a dose of the Sinovac's CoronaVac vaccine to a teenager in Pretoria, South Africa, Sept. 10, 2021. Chinese pharmaceutical company Sinovac Biotech on Friday launched the Phase III clinical trial of its COVID-19 vaccine on a group of children and teenagers between six months and 17 years old in South Africa. (Photos: Xinhua)

A medical worker shows a dose of the Sinovac's CoronaVac vaccine in Pretoria, South Africa, Sept. 10, 2021. Chinese pharmaceutical company Sinovac Biotech on Friday launched the Phase III clinical trial of its COVID-19 vaccine on a group of children and teenagers between six months and 17 years old in South Africa.

People applauds after a medical worker administers a dose of the Sinovac's CoronaVac vaccine to a teenager in Pretoria, South Africa, Sept. 10, 2021. Chinese pharmaceutical company Sinovac Biotech on Friday launched the Phase III clinical trial of its COVID-19 vaccine on a group of children and teenagers between six months and 17 years old in South Africa.