There were 35,670 suspected reinfection among the 2.8 million people who tested positive last month.
A preliminary study by South African scientists published on Thursday found that the Omicron variant was three times more likely to cause reinfection than the Delta or Beta strains.
The findings are based on data collected by the country’s health system, providing the first epidemiological evidence of Omicron’s ability to ward off immunity from previous infection.
The article was uploaded on a medical preprint server and has not been peer-reviewed.
There were 35,670 suspected reinfection cases among the 2.8 million people who tested positive as of November 27. Cases are considered reinfected if they test positive 90 days apart. .
“Recent episodes of reinfection have occurred in people whose primary infection occurred on all three,” said Juliet Pulliam, Director of the Center for Epidemiological Analysis and Modeling at DSI-NRF South Africa. wave, in which the most people are infected is the Delta episode.
Pulliam cautions that the authors do not have information on the immunization status of individuals and therefore cannot assess the extent to which Omicron evades vaccine-induced immunity. The researchers plan to study this further.
“Data are also urgently needed on disease severity associated with Omicron infections, including in people with a history of infection,” she said.
Michael Head, a scientist at the University of Southampton, hailed the research as “high quality”.
“This analysis seems very disturbing, with immunity from previous infections being relatively easily overlooked. Could all of this still be a ‘false alarm’? That’s increasingly true? less likely,” he said in a statement.
Exponentially increasing
Earlier, South Africa’s top scientist Anne von Gottberg, an expert at the National Institute of Infectious Diseases, had forecast an increase in the number of cases, but authorities expect the vaccine to still be effective against diseases. serious results.
“We believe the number of cases will increase exponentially in all provinces of the country,” she told a news conference with the World Health Organization Africa region.
She added: “We believe vaccines will still protect against severe diseases.
“Vaccines are always protective against serious illness, hospitalization and death.”
WHO experts reiterated calls for a rethink of travel bans for southern Africa, as Omicron has now been reported in nearly two dozen countries and its source remains unclear.
“South Africa and Botswana discovered this variant. We don’t know where it originated,” said expert Ambrose Talisuna. “To punish people who just find out or report … is not fair.”
By mid-November, South Africa was reporting around 300 cases a day. On Wednesday, the country reported 8,561 new cases, up from 4,373 the day before and 2,273 on Monday.
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