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Omicron may cut future severity of COVID and protect against the Delta variant, South Africa study finds

January 18, 2022, 3:58 PM UTC

A strong wave of coronavirus infections driven by the Omicron variant could hasten the end of pandemic disruptions as it appears to cause less severe illness and provides protection against the Delta variant, South Africa-based researchers said. 

A laboratory study that used samples from 23 people infected with the Omicron variant in November and December found that while those who previously caught the Delta variant could contract Omicron, those who get the Omicron strain couldn’t be infected with Delta, particularly if they have been vaccinated, the researchers said. Results among the unvaccinated were unclear, as was whether they had been previously infected.

While Omicron is significantly more infectious than Delta, hospital and mortality data in countries including South Africa—the first country to experience a wave of Omicron infections—appears to show that it causes less severe disease. The study—an update to one conducted last year—suggests that Omicron can displace Delta, the researchers led by Alex Sigal of the Africa Health Research Institute said.

“The implications of such displacement would depend on whether Omicron is indeed less pathogenic than Delta,” the researchers said. “If so, then the incidence of COVID-19 severe disease would be reduced and the infection may shift to become less disruptive to individuals and society.”

The study has been published as a pre-print and has yet to be peer-reviewed.

In South Africa, deaths during the Omicron wave peaked at about 15% of the rate seen during the Delta-driven surge, while hospitalizations peaked at 60% of the influx caused by Delta, according to the National Institute for Communicable Diseases.

Of the 23 participants, 14 were admitted to the hospital, but only one needed supplemental oxygen, the researchers said. Ten had been vaccinated, either with shots produced by Pfizer Inc. or Johnson & Johnson, but still got infected with Omicron.

World Health Organization Chief Scientist Soumya Swaminathan stressed that the study showed Omicron gave protection against Delta only in people who were vaccinated.

“Infection is not a substitute for vaccination, as some are suggesting,” Swaminathan said in a tweet.

Omicron was also tested against 18 samples taken from 14 people previously infected with Delta and showed “extensive escape” from antibodies, the researchers said.

—With assistance from Thomas Mulier.

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