With Omicron, reinfection is three times more likely: South African health body

The new Omicron variant of the coronavirus carries a threefold higher risk of reinfection than the currently dominant Delta or Beta variant, a South Africa group of health organisations said on Thursday.

According to the South African Centre for Epidemiological Modelling and Analysis (SACEMA) and the National Institute of Communicable Diseases (NICD), based on the data collected by the health system, the results provide the first epidemiological evidence about the ability of Omicron to evade immunity following prior infection.

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They released the statement after a group of South African health organisations published a paper on medrxiv.org as a pre-print, which means it had not yet been peer-reviewed.

Microbiologist Anne von Gottberg of the National Institute for Communicable Diseases echoed this, during an online news conference hosted by the World Health Organization earlier that day, she said South Africa was seeing a rise in COVID-19 reinfections caused by Omicron.

Daily reports of Coronavirus infections have suddenly risen in South Africa, with the government reporting 11,535 new infections on Thursday, up from 312 ten days ago.

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NICD, one of a wider network of health organisations that do genome sequencing on samples, said on Wednesday that the Omicron variant is getting around immunity and fast becoming the dominant variant in the country.

The NICD said in a statement on Thursday that the "reinfection risk profile of Omicron is substantially higher than that associated with the Beta and Delta variants during the second and third waves." 

The study used routine surveillance data from March 2020 to November 27. It is based on a sample of 2,796,982 individuals with positive results at least 90 days prior to November 27, of which 35,670 were suspected reinfections.

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If the newly emerged variant is causing more reinfections than new infections, it indicates it has developed the ability to evade natural immunity from previous infections.

According to Juliet Pulliam, director of SACEMA and author of the pre-print paper, Omicron's pattern will likely be established by early to mid-December in all provinces of South Africa.

"Recent reinfections have occurred in individuals whose primary infections occurred across all three waves, with the most having their primary infection in the Delta wave," she tweeted.

Pulliam cautioned, however, that since the authors did not have information about the individuals' vaccination status, they were unable to assess whether Omicron evades vaccination-induced immunity, or to what extent. Further research will be undertaken into this question.

(With inputs from agencies)