By Antony Sguazzin

New omicron sublineages show an ability to evade antibodies from earlier infection and vaccination, a South African laboratory study has found.

The findings could signal a fresh wave of infections by the BA.4 and BA.5 sublineages of the omicron variant that were discovered this month in South Africa.

Blood samples from people who had been infected with the original omicron variant saw an almost eightfold drop in neutralizing antibody production when tested against the BA.4 and BA.5 sublineages, the study, led by the Africa Health Research Institute in South Africa, showed.

Samples from people who were vaccinated showed about a threefold decrease, according to the study.

“The low absolute neutralization levels for BA.4 and BA.5, particularly in the unvaccinated group, are unlikely to protect well against symptomatic infection,” the researchers said in the study, which is yet to be peer reviewed. “This may indicate that, based on neutralization escape, BA.4 and BA.5 have potential to result in a new infection wave.”

The results of the study come amid a fresh surge of infections in South Africa, which was the first country to experience a wave of cases caused by omicron after the variant was first identified in the country and neighboring Botswana.

On Saturday South Africa recorded 6,527 new cases and a test positivity rate of 21.5%. That compares with 581 cases and a positivity rate of 4.5% on March 28.

While hospitalizations are rising gradually, there hasn’t been a noticeable increase in deaths, Waasila Jassat, a public health specialist at South Africa’s National Institute of Communicable Diseases, said on Friday.

The study used samples from 24 people who had been infected with the original omicron variant but hadn’t been vaccinated. It also tested the sublineages against samples from 15 vaccinated people, eight of whom had Pfizer Inc.’s shots and seven whom had received Johnson & Johnson’s vaccines.

Africa Health Research Institute’s laboratory, which is in Durban and led by Alex Sigal, was the first to test the original omicron variant against blood samples, showing Pfizer’s shot was less effective against it than against earlier variants.

With more than 100,000 official deaths from Covid-19, and three times that if excess death data is taken into account, South Africa is the worst hit country in Africa. Still, most African countries have weak health systems that fail to identify most infections or attribute the causes of death accurately.