South Africa has scrapped plans to use the Oxford-AstraZeneca coronavirus vaccine because it "does not prevent mild to moderate disease" of the variant that has spread widely in the country, the government said.

Health minister Zweli Mkhize announced that front-line healthcare workers will be given the unapproved Johnson & Johnson vaccine from next week as part of a study to see what protection it provides, particularly against the South African variant.

The single-shot Johnson & Johnson vaccine is still being tested internationally and has not been approved in any country.

In a nationally broadcast address, Mr Mkhize declared that the vaccine is safe, relying on tests of 44,000 people carried out in South Africa, the United States and Latin America.

The Johnson & Johnson vaccines will be used to launch the first phase of South Africa's vaccination drive in which the country's 1.25 million health care workers will be inoculated, he said, adding that the medical workers will be closely monitored to see what protection they get from the inoculation.

"The Johnson & Johnson vaccine has been proven effective against the 501Y.V2 variant (dominant in South Africa) and the necessary approval processes for use in South Africa are under way," said Mr Mkhize.

"The rollout of vaccination will proceed in the form of an implementation study with the partnership of the Medical Research Council and the National Department of Health vaccination sites across the country.

"This will provide valuable information about the pandemic in the post-vaccination community and thus, ensure early identification of breakthrough infections should they occur amongst vaccinated health workers."

Those vaccine shots will be followed by a campaign to vaccinate an estimated 40 million people in South Africa by the end of the year.

Mr Mkhize said South Africa will be using the Pfizer vaccine and others, possibly including the Russian Sputnik V and the Chinese Sinopharm vaccine.