South Africa has offered its stock of Oxford-AstraZeneca Covid-19 vaccines to the African Union, a senior health official said, as the country pivots to using shots developed by Johnson & Johnson instead.

The country paused its rollout of the Oxford-AstraZeneca vaccine after preliminary trial data showed it offered minimal protection against mild to moderate illness caused by the variant of the virus that emerged in South Africa last year.

"The AU will distribute to those countries who have already expressed interest in acquiring the stock," South African Health Minister Zweli Mkhize told lawmakers in Cape Town on Tuesday.

Mkhize said that rumours the shots, which were purchased from the Serum Institute of India (SII), had expired and were being returned to India were "simply not true," and no money was wasted.

"The recent announcement around the limited efficacy of the AstraZeneca vaccine, which we had already procured, was certainly disappointing; however we were determined not to be derailed from our commitment to roll out vaccines in February," Mkhize said.

The health minister announced that the country had instead secured 9 million doses of the Johnson & Johnson vaccine.

Developed by Janssen, Johnson & Johnson's Belgium-based vaccine division, the single-dose vaccine has shown to be effective in preventing moderate and severe disease from South Africa's dominant coronavirus variant with an efficacy of 57% in trials conducted in South Africa.

The B.1.351 variant was responsible for 95% of cases in that trial and has now appeared in more than 44 countries. "We have actually secured enough doses to vaccinate all the people who will need to be vaccinated in South Africa," said Mkhize.

South Africa is expected to green-light the Johnson & Johnson vaccine and begin administering doses this week. The rollout marks a 180-degree pivot by South Africa, which had received 1 million doses of the Oxford-AstraZeneca Covid-19 vaccine and planned to begin administering doses to health care workers in February.

Another 500,000 Oxford-AstraZeneca doses were due to be delivered by the end of the month. Instead, South Africa has switched to a new plan. It will start vaccinating health care workers with Johnson & Johnson shots in a research study.

Officials will administer shots to health workers at 20 vaccination centres in each of the country's nine provinces. More than 380,000 health workers have registered so far.

The first batch of 80,000 Johnson & Johnson shots are expected to this week, with delivery of 500,000 doses in the next four weeks, Mkhize said. That will be supplemented by an additional 20 million doses of the Pfizer vaccine, anticipated in late March.

South Africa has been consulting with scientists about what to do with the AstraZeneca vaccine following news that two doses provided "substantially reduced" protection against mild to moderate Covid-19 disease from the B.1.351 variant.

It was a damaging setback for efforts to curtail the pandemic in South Africa, the hardest-hit country on the continent. More than 48,000 people are known to have died from Covid-19 there, and overall cases, which have topped 1.4 million, are now largely being driven by the new variant.

Seven other countries are now reporting the B.1351 variant in Africa -- including Ghana, Kenya, Comoros, Botswana, Mozambique and Zambia.It was not clear from the study, which has not yet been peer reviewed, whether the Oxford-AstraZeneca vaccine protected against severe disease from the B.1.351 variant.

The 2,000 clinical trial participants were mostly young healthy adults and therefore unlikely to become severely ill. But based on immune responses detected in their blood samples, the researchers said there was "still some hope" that the vaccine could protect against more severe cases.

AstraZeneca recently said it is working with Oxford University to adapt the vaccine against the B.1.351 variant and that it would advance it through clinical development to make it "ready for autumn delivery should it be needed."

Professor Salim Abdool Karim, who is a co-chair of South Africa's Covid-19 advisory committee, had initially told CNN that the country would likely adopt a "stepped approach," in which they assessed the impact of the Oxford-AstraZeneca vaccine as it is rolled out.

But it appears that the country has now scrapped that strategy entirely.In regard to the future role of Oxford-AstraZeneca in South Africa, Mkhize said only that health officials would continue to be guided by experts and led by science.

It's a big blow for the Oxford-AstraZeneca vaccine, which has been hailed for its low cost and easy storage as one of the world's best hopes for defeating the virus. The COVAX program -- a coalition that includes Gavi and the World Health Organization with the aim of distributing Covid-19 vaccines to poorer countries -- is reliant on the Oxford-AstraZeneca vaccine.

Earlier this month, COVAX announced a plan to distribute more than 337 million Covid-19 vaccine doses worldwide -- of which 336 million doses are the AstraZeneca-Oxford vaccine and just 1.2 million doses are the Pfizer-BioNTech vaccine.

WHO authorized the Oxford-AstraZeneca vaccine for emergency use on Monday, after encouraging its use even in countries where variants of the coronavirus are circulating."While a vaccine that protects against all forms of Covid-19 illness is our biggest hope, preventing severe cases and hospitalizations which overwhelm hospitals and health systems is crucial," Dr. Matshidiso Moeti, the WHO regional director for Africa, said at a news briefing Thursday.

The second wave of Covid-19 in Africa, which peaked in January, was more deadly than the first wave, according to Dr. Moeti.With the rollout of vaccines, "if cases remain mostly mild and moderate and don't require critical care then we can save many lives," she added.