A preliminary study by South African scientists published Thursday suggests the Omicron variant is three times more likely to cause reinfections compared to the Delta or Beta strains, news agency AFP has reported.
The findings, based on data collected by the country's health system, provides the first epidemiological evidence about Omicron's ability to evade immunity from prior infection.
The researchers also cautioned that they did not have information about the vaccination status of the individuals studied and therefore could not assess to what extent Omicron evades vaccine-induced immunity. The researchers plan to study this next.
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Earlier, South African scientists forecast a surge in cases but said authorities expected vaccines would still be effective against severe outcomes.
In mid-November, South Africa was reporting about 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.
Several countries rushed to clamp travel ban from South Africa and other African countries after the new variant was detected.
The WHO has reiterated calls for a rethink on travel bans against southern Africa, given that Omicron had now been reported in nearly two dozen countries and its source remained unclear.