JOHANNESBURG (AP) — South Africa is considering giving a COVID-19 vaccine that is still in the testing phase to health workers, after suspending the rollout of another shot that preliminary data indicated may be only minimally effective against the mutated form of the virus dominating the country.

The country was scrambling Monday to come up with a new vaccination strategy after it halted use of the AstraZeneca vaccine — which is cheaper and easier to handle than some others and which many had hoped would be crucial to combatting the pandemic in developing countries. Among the possibilities being considered: mixing the AstraZeneca vaccine with another one or giving Johnson & Johnson's single-dose vaccine, which has not yet been authorized for use anywhere, to 100,000 health care workers while monitoring its efficacy against the variant.

The abrupt change in strategy was prompted by preliminary results in a small study that showed the AstraZeneca vaccine was only minimally effective against mild to moderate cases of the disease caused by the variant.

There is reason to hope the Johnson & Johnson vaccine may fare better in the country. Initial results from an international test of the vaccine showed it is 57% effective in South Africa at preventing moderate to severe COVID-19. That was less than in other countries — the rate was 72% in the U.S., for example — presumably due to the worrisome variant. It was even more effective — 85% internationally — at preventing the most serious symptoms.

“We can’t wait. We already have good local data,” said Dr. Glenda Gray, director of the South Africa Medical Research Council, who led the South African part of the global trial. She stressed that clinical trials show that the J&J vaccine is safe. Like AstraZeneca's, it is also easier to handle than the frozen vaccines from Pfizer and Moderna.

South Africa appears to be heeding her call. She said the country is making urgent plans to “roll it out and evaluate it in the field.”

South Africa’s inoculation strategy is being watched globally because the variant first detected and now dominant here is spreading in more than 30 countries. Officials say this form of the virus is more contagious, and evidence is emerging that it may be more virulent; recent studies have also shown it can infect people who have survived the original form of the virus.

After a second surge, cases and deaths in South Africa have begun to fall recently, but it is still battling one of Africa’s most severe outbreaks, with more than 46,000 deaths. It is worried that another spike will come in May or June, when the Southern Hemisphere country heads into its winter.

“Our scientists must get together and quickly figure out what approach we’re going to use,” Health Minister Zweli Mhkize said Sunday night, announcing the suspension of the use of the AstraZeneca vaccine, which is currently the only one available in South Africa. Deliveries of others, including the one made by Pfizer and BioNTech, are expected soon.

The suspension threw South Africa's vaccination plans into disarray just one week after the country received its first 1 million doses of the vaccine. It came after the early results of a small clinical trial showed that the shot offered only minimal protection against mild to moderate cases of COVID-19 in young adults, according to an announcement by the University of Witwatersrand, which conducted the test.

The AstraZeneca study involved 2,000 healthy volunteers with a median age of 31. Scientists generally like to see larger studies before drawing conclusions, and experts say the vaccine may still prevent severe disease — and that would go a long way in slowing the pandemic and avoiding hospitals from becoming overwhelmed with patients.

“Vaccines that are effective against the more severe forms of disease may not affect milder forms, so there is optimism that severe disease will still be prevented by vaccines,” said Peter Openshaw, a professor of experimental medicine at Imperial College London.

But the results were disappointing enough that South African officials decided to postpone the rollout of the vaccine, which was supposed to be given to front-line healthcare workers starting in mid-February.

The preliminary study has not been peer-reviewed — the gold standard in scientific studies — but was still “a reality check,” said Professor Shabir Madhi, who conducted the trial. “We were euphoric. We must recalibrate our expectations."

Now, the country is looking to switch gears. It may end up continuing with giving at least one dose of AstraZeneca in the hope it will protect against severe disease and death from the variant. It is also considering combining the shot with one from another vaccine. Most of the vaccines being tested require two doses; Johnson & Johnson is an exception.

An experimental study began last week in Britain testing whether doctors could safely mix and match doses of the AstraZeneca vaccine with the shot made by Pfizer.

An added complication is that the AstraZeneca doses in South Africa have an April expiration date, making it difficult to administer two doses within such a short period.

Last week, Sarah Gilbert of Oxford University, who helped develop the AstraZeneca vaccine, said researchers were currently working to tweak their vaccine by inserting a genetic sequence from the new variant.

South African experts have been conducting clinical trials on the effects of the variant, known as B.1.351. That variant quickly became more than 90% dominant here.

The variant has reduced the level of protection offered by virtually all the vaccines, but most vaccines show satisfactory efficacy in protecting against severe cases and death caused by the version, said Madhi. Trials of the Novavax vaccine, for instance, showed diminished but still good protection against the variant, he said.

“It is not all doom and gloom … we do have vaccines that work,” said Madhi.

Still, he added, “This virus is likely to be with us for the course of our lifetimes. It is unlikely that it will be eradicated soon.”

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Associated Press Medical Writers Maria Cheng in London and Lauran Neergaard in Alexandria, Virginia.

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This story was first published on Feb. 8, 2021. It was updated on Feb. 9, 2021, to correct that the Moderna vaccine needs to be stored at regular freezer temperatures, not super-frozen temperatures.

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Follow all of AP’s pandemic coverage at https://apnews.com/hub/coronavirus-pandemic, https://apnews.com/hub/coronavirus-vaccine and https://apnews.com/UnderstandingtheOutbreak.