South Africa has asked the Serum Institute of India to take back the one million COVID-19 vaccine doses the company had sent in early February, The Economic Times reported on Tuesday, a week after the country said it will put on hold use of AstraZeneca's shot in its vaccination program.

Serum Institute of India, which is producing AstraZeneca's shot, has emerged as a key vaccine supplier. One million doses of the COVID-19 vaccine landed in South Africa last week and another 500,000 were due to arrive in the next few weeks.

The company did not immediately respond to a Reuters request for comment.

South Africa's health minister has said the government may sell doses of AstraZeneca's vaccine, after the country paused its rollout following a small clinical trial that showed it offered minimal protection against mild to moderate illness from the 501Y.V2 coronavirus variant dominant in the country.

AstraZeneca has said its vaccine appeared to offer only limited protection against mild disease caused by the South African variant, based on data from a study by South Africa's University of the Witwatersrand and Oxford University.

The African country, which is yet to launch its COVID-19 vaccination program, has decided to start vaccinating health workers with Johnson & Johnson's vaccine in the form of an "implementation study" with researchers.