A preliminary study by South African scientists published on Thursday suggests that the Omicron variant is three times more likely to cause reinfection than delta or beta strains.
The findings, based on data collected by the country’s health system, provide the first epidemiological evidence about Omicron’s ability to ward off immunity from prior infection.
The paper was uploaded to a medical preprint server and has not yet been reviewed.
There were 35,670 suspected re-infections among the 2.8 million individuals who tested positive as of 27 November. Cases are considered to be re-infection if they test positive 90 days apart.
Juliette Pulliam, director of South Africa’s DSI-NRF Center of Excellence in Epidemiological Modeling and Analysis, tweeted: “Recently there has been an infection in people who have had a primary infection in all three waves, with the most primary infection in the delta wave. Has happened.”
Pulliam cautioned that the authors did not have information on the vaccination status of individuals and therefore could not assess the extent to which Omicron evades vaccine-induced immunity. The researchers plan to study this further.
“There is also an urgent need for data on disease severity associated with Omicron infection, including in individuals with a history of prior infection,” she said.
Michael Head, a scientist at the University of Southampton, praised the research as “high quality”.
“This analysis seems very worrying, given immunity from past infections being bypassed relatively easily. Could all this still be a ‘false alarm’? The likelihood of this seems less and less,” he said in a statement. Is.”
Earlier, South Africa’s top scientist Anne von Gottberg, an expert at the National Institute for Communicable Diseases, forecast a rise in cases, but said officials still hope the vaccines will be effective against dire consequences.
“We are confident that the number of cases will increase rapidly in all the provinces of the country,” she told a news conference with the World Health Organization’s Africa region.
“We believe that vaccines will still protect against serious disease,” she said.
“Vaccines have always been put in place to protect against serious illness, hospitalization, and death.”
WHO experts reiterated calls for a rethinking of travel restrictions against southern Africa, noting that Omicron was now reported in nearly two dozen countries and its source remained unclear.
“South Africa and Botswana traced the variant. We don’t know where it may have originated,” expert Ambrose Talisuna said. “Punishing people who are just finding out or reporting … is unfair.”
In mid-November, South Africa was reporting around 300 cases a day. On Wednesday, the country reported 8,561 new cases, up from 4,373 a day earlier and 2,273 on Monday.