Reinfections 3 times more likely with Omicron: Study

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.

New Delhi: 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 findings, based on data collected by the country's health system, provide the first epidemiological evidence about Omicron ability to evade immunity from prior infection. Also, the analysis was uploaded on a medical preprint server and hasn't 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.

Pulliam cautioned that the authors did not have information about the individuals' vaccination status and therefore could not assess to what extent Omicron evades vaccine-induced immunity. The researchers plan to study this next. "Data are also urgently needed on disease severity associated with Omicron infection, including in individuals with a history of prior infection," she said.

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.

Earlier, top South African scientist Anne von Gottberg, an expert at the National Institute for Communicable Diseases, forecast a surge in cases but said authorities expected vaccines would still be effective against severe outcomes.

For the first time on Thursday, two cases of Omicron variant have been detected through INSACOG in Karnataka, which was confirmed by the Union Health Ministry. Both the patients are men aged 66 years and 46 years with mild symptoms. Severe symptoms have not been noted, a central government official said during a press conference here.

Health Ministry also urged people not to panic, instead follow Covid-appropriate behaviour and get vaccinated without delay.