Friday, January 21

Severity in microns seen masked by a previous 72% case rate in SA

Leading scientists warned that the level of immunity against coronavirus among the South African population due to previous infections may be masking the severity of the disease caused by the omicron variant.

Since the discovery of the variant was announced in South Africa and Botswana on November 25, hospitalization rates in South Africa have increased, albeit at a much slower rate than in previous waves, even as cases are increasing more rapidly. The number of deaths has also been lower.

A recent seroprevalence survey in Gauteng, the South African province where the omicron variant was first identified, showed that 72% of the population had a prior infection with the coronavirus, said Shabir Madhi, a vaccinologist at the University of the Witwatersrand. That compares with about 20% when the beta variant emerged a year ago, said Madhi, who led the testing of the injections for AstraZeneca Plc and Novavax Inc. in South Africa.

“The evolution of the omicron variant comes at a very different stage of the pandemic,” Madhi said in an interview with the Global Health Crisis Coordination Center. “It is important to have it in the back of our minds when we see what is unfolding in South Africa and what we might see in other settings, which could have a very different epidemiology.”

Inadvertent infections

Official statistics do not reflect the extent of the pandemic’s impact in South Africa, with only 3.2 million positive tests and around 90,000 deaths. Excess deaths, a measure of mortality compared to a historical average, shows that about 275,000 people may have died from the disease.

The disparity between official statistics and the possible spread of infections is most pronounced in South Africa, although not unique. The US Centers for Disease Control estimate that during the course of the pandemic through September, there were 146.6 million infections and 921,000 deaths as a result of Covid-19. Official statistics show more than 50 million infections and 799,000 deaths.

Madhi’s hypothesis is supported by other scientists.

“You have big pockets of population immunity,” Tulio de Oliveira, who runs two gene sequencing institutes in South Africa, said in an interview with CBS News on December 12. “We will have to separate whether mild cases are due to young people becoming infected or whether the immunity of the population prior to infection and vaccination are responsible for reducing the number of people hospitalized.”

About 6,000 people are hospitalized in South Africa with Covid-19, about a third of the number at the peak of the second and third waves of infection. Current daily cases are approaching record levels.

“That could really be due to the fact that immunity in the country is high, either from natural immunity, from past infections or from vaccines,” said Barry Schoub, chairman of the South African Vaccine Ministerial Advisory Council, in an interview with Sky News. .

Of the 60 million people in South Africa, about 26% are fully vaccinated. That compares with 70% in the UK.

While omicron has shown, in early studies, that it can evade antibodies produced by vaccines or previous infections more easily than previous variants, Madhi says that immunity may come from the protection of T cells, which kill infected cells.

“In South Africa, there is apparently significant population protection against severe Covid due to the basis of T-cell immunity, even though omicron is antibody elusive,” he said in a text message.

Beta variant

South Africa’s experience with omicron may once again raise the concept of so-called herd immunity, whereby a sufficient number of the population has been vaccinated or previously infected to mitigate the impact of waves of infection. Still, the coronavirus’s ability to mutate and the different paths the pandemic has taken around the world can make that elusive.

“The data coming out of South Africa is really very encouraging,” said Sam Fazeli, senior pharmaceutical industry analyst at Bloomberg Intelligence. “Let’s not forget that South Africa had a wave of infections with the beta variant, which was not seen anywhere else. This can make a difference in the response to omicron. “

© 2021 Bloomberg

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