Study suggests past COVID infection may not fend off omicron

A research group has been tracking reinfections in South Africa and reported a jump with the arrival of omicron that they hadn’t seen when two previous variants, including the extra-contagious delta variant, moved through the country.

The findings, posted online Thursday, are preliminary and haven’t yet undergone scientific review. Nor did the researchers say what portion of the reinfections were confirmed as omicron cases — or whether they caused serious illness.

But the timing of the reinfection spike suggests that omicron “demonstrates substantial population-level evidence for evasion of immunity from prior infection,” they wrote.

“Previous infection used to protect against delta, and now with omicro,n it doesn’t seem to be the case,” one of the researchers, Anne von Gottberg of the University of Witwatersrand, said at a World Health Organization briefing on Thursday. ...