■ South Africa might give a COVID-19 vaccine in the testing phase to health workers.

Drops Astrazeneca after finding it ineffective against variant

JOHANNESBURG — 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 thecountry.

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 been authorized for use anywhere, to 100,000 health care workers while monitoring its efficacy against the variant.

The 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 percent effective in South Africa at preventing moderate to severe COVID-19. That was less than in other countries — the rate was 72 percent in the U.S., for example — presumably due to the worrisome variant. It was even more effective — 85 percent 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 super-frozen vaccines from Pfizer and Moderna.

The head of the World Health Organization said Monday the emergence of new COVID-19 variants has raised questions about whether or not existing vaccines will work, calling it “concerning news” that the vaccines developed so far may be less effective against the variant first detected in South Africa.

Tedros Adhanom Ghebreyesus said it was increasingly clear that vaccine manufacturers would need to tweak their existing shots to address the ongoing genetic evolution of the coronavirus, saying booster shots would most likely be necessary, especially since new variants of the virus are now spreading globally and appear likely to become the predominant strains.

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.