According to a preliminary study published Thursday by South African scientists, the Omicron variety is three times more likely to induce reinfections than the Delta or Beta variants.
The findings, which are based on data collected by the country’s health system, are the first epidemiological evidence of Omicron’s potential to overcome prior infection immunity.
The paper has not yet been peer-reviewed and was uploaded to a medical preprint server.
Up to November 27, there were 35,670 possible reinfections among 2.8 million people who had positive testing. If two cases tested positive 90 days apart, they were considered reinfections.
Juliet Pulliam’s Tweet
“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,” Juliet Pulliam, director of the DSI-NRF Centre of Excellence in Epidemiological Modelling and Analysis in South Africa, tweeted.
Pulliam noted that the authors were unable to determine the extent to which Omicron evades vaccine-induced immunity because they did not have information about the individuals’ vaccination status. The researchers intend to examine this further.
“Data are also urgently needed on disease severity associated with Omicron infection, including in individuals with a history of prior infection,” she said.
“High quality”, praises Michael Head
The research was praised as “high quality” by Michael Head, a scientist at the University of Southampton.

In a statement, he stated, “This analysis does look very concerning, with immunity from previous infections being relatively easily bypassed. Might this all still be a ‘false alarm’? That is looking less and less likely.”
Anne Von Gottberg says
Earlier this week, top South African scientist Anne von Gottberg, an expert at the National Institute for Communicable Diseases, predicted a spike in cases, but claimed immunizations would still be effective against severe consequences.
“We believe the number of cases will increase exponentially in all provinces of the country,” she said during a press conference with the WHO’s Africa region.
“We believe that vaccines will still however protect against severe disease,” she continued.
“Vaccines have always held out to protect against serious disease, hospitalisations and death.”
What WHO experts says
Given that Omicron had already been reported in over two dozen countries and its origins remained unknown, WHO experts called for a reassessment on travel bans against southern Africa.
“South Africa and Botswana detected the variant. We don’t know where the origin of this could have been,” Ambrose Talisuna, a specialist, remarked. “To punish people who are just detecting or reporting… is unfair.”

South Africa was reporting roughly 300 cases per day in mid-November. The country reported 8,561 new cases on Wednesday, up from 4,373 the day before and 2,273 the day before.
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