A preliminary study by South African scientists suggests that the Omicron variant is associated with a substantial ability to evade immunity from prior infection and is three times more likely to cause reinfections compared to the Beta or Delta variants. There were 35,670 suspected reinfections among nearly 2.8 million individuals with positive test results for coronavirus disease (Covid-19). Those who tested positive for Covid 90 days apart were considered to have suspected reinfections.
The paper is available on a medical preprint server and has not yet been peer-reviewed.
"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," tweeted Juliet Pulliam, director of the South African DSI-NRF Centre of Excellence in Epidemiological Modelling and Analysis.
The researchers also observed a recent surge in the number of reinfections in individuals who already had multiple suspected infections from mid-November. The study may have significant implications for public health measures, particularly in countries with high rates of immunity from prior infection.
{{/usCountry}}The researchers also observed a recent surge in the number of reinfections in individuals who already had multiple suspected infections from mid-November. The study may have significant implications for public health measures, particularly in countries with high rates of immunity from prior infection.
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Pulliam said the authors didn’t have information about the vaccination status of individuals with suspected reinfections and therefore could not assess whether Omicron also evades vaccine-derived immunity. The scientists are planning to quantify the extent of Omicron’s immune escape for both natural and vaccine-derived immunity.
“Data are also urgently needed on disease severity associated with Omicron infection, including in individuals with a history of prior infection,” Pulliam wrote.
Praising the research as "high quality”, Michael Head, a scientist at the University of Southampton, said that the analysis look “very concerning”.
“Might this all still be a 'false alarm'? That is looking less and less likely," he said in a statement, reported news agency AFP.