Scientists from South Africa published a preliminary study on Thursday that suggested that the Omicron variant is three times more likely to cause reinfections compared to the Delta or Beta strains. Based on the findings of the data collected by the country’s health system, information related to the first epidemiological evidence about Omicron’s ability to evade immunity from prior infection was provided. The paper has not yet been peer-reviewed and was uploaded on a medical preprint server.
Until November 27, there were 35,670 suspected reinfections among 2.8 million individuals with positive tests. If the cases were tested positive 90 days apart, cases were considered reinfections.
Director of the South African DSI-NRF Centre of Excellence in Epidemiological Modelling and Analysis, Juliet Pulliam tweeted, “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.”
Pulliam cautioned that the authors did not have information about the individuals’ vaccination status. Therefore the researchers plan to study to what extent Omicron evades vaccine-induced immunity next.
She said, “Data are also urgently needed on disease severity associated with Omicron infection, including in individuals with a history of prior infection.”
A scientist at the University of Southampton, Michael Head praised the research as “high quality.” He said in a statement, “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.”