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Health workers with a COVID-19 patient at Green-acres Hospital in Port Elizabeth, South Africa on Nov. 18, 2020.SAMANTHA REINDERS /The New York Times News Service

A new variant of COVID-19 that is inflicting heavy damage across Southern Africa can evade the immunity that is normally provided by previous infection, researchers are discovering.

The research is the latest to raise questions about the dangers of the new variants that were detected in South Africa, Britain and Brazil in recent weeks. Scientists have already warned that the new variants are about 50 per cent more transmissible than earlier variants.

“The ability of the virus to evolve may have been underestimated,” said Alex Sigal, a scientist at the Africa Health Research Institute and co-author of a pre-print paper published on Thursday.

People who recover from the coronavirus are usually protected from being infected a second time, because they develop neutralizing antibodies in their blood.

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But the mutations in the new variant detected in South Africa, known as 501Y.V2, “may have caused the virus to lose a great deal of sensitivity to previous antibody immunity,” Dr. Sigal said in an article released by the institute.

The variant, first detected in October, has quickly become the dominant variant in most of South Africa, fuelling a dramatic surge of cases in the past two months. It has also been detected in 23 countries worldwide. Although the variant is not believed to be deadlier than previous variants, the soaring number of cases has led to a similar rise in hospitalizations and deaths.

The total number of COVID-19 deaths in South Africa has jumped by 37 per cent in the past three weeks. The country was shocked on Thursday by the death of a popular cabinet minister, Jackson Mthembu, who had announced only 10 days ago that he had tested positive for the virus.

The full extent of the new variant’s spread outside South Africa is unclear. But large numbers of travellers and migrants crossed borders in Southern Africa during the holiday season, and there has been an extraordinary rise in COVID-19 cases since then.

In countries such as Zimbabwe, Lesotho and Malawi, located near South Africa, the new cases this month are so numerous that they represent more than half of all cases ever recorded in those countries since the beginning of the pandemic. In Zambia, the new cases this month represent nearly half of all cases since the start of the pandemic.

The virus has also claimed the lives of several cabinet ministers in Zimbabwe and Malawi this month, including the Zimbabwean foreign minister, Sibusiso Moyo.

It is still unclear whether the COVID-19 vaccines will be fully effective against the new variants, or whether the vaccines might need to be modified. Studies to be published in South Africa in the next few days or weeks should help to answer that crucial question, and their results will have “global importance,” according to Shabir Madhi, a prominent South African vaccinology professor, who was speaking in an online briefing on Thursday.

In the paper published on Thursday, the South African scientists described how they had tested blood plasma that contained antibodies from people who had recovered from COVID-19 after being infected in the pandemic’s first wave last year. By testing it against the new variant, they found that the antibodies from these people were much less effective in neutralizing the new variant.

Compared with first-wave variants, the scientists needed at least a sixfold higher plasma concentration, and up to 200 times higher, to neutralize the new variant in a lab setting.

The authors said the new data were worrisome, but they also noted that the vaccines could still produce a broader antibody response that will protect people against the new variants. They emphasized that vaccination is still absolutely recommended.

Earlier this week, South African scientists reported on similar research that showed a significant risk of reinfection from the new variant for people who had been infected by earlier variants. Of the 44 people in the study, 21 had no detectable neutralization activity when their plasma was tested against the new variant.

“The blood samples from half the people we tested showed that all neutralizing activity was lost,” said a report this week by South Africa’s National Institute for Communicable Diseases. “This suggests that they may no longer be protected from reinfection.”

Researchers also examined South Africa’s data on COVID-19 tests. They found 4,000 potential cases of reinfection, where people had twice tested positive for the virus, with a minimum 90-day interval between the tests.

It appears that the mutations in the new variant “have allowed the virus to become resistant to antibody neutralization,” the South African institute said.

This means it is important for people to continue to wear masks and adhere to physical distancing, even if they have been infected with the virus before, it said.

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