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The work has not yet been peer-reviewed and was uploaded to a medical preprint server.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 deemed reinfections.
“Recent reinfections have occurred in persons who had main infections in all three waves, with the majority 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 investigate 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.
Michael Head, a scientist at the University of Southampton, praised the research as “high quality.”
“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,” he said in a statement.
