South Africa study finds Omicron carries 80% lower risk of hospitalization and 70% lower risk of severe disease

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If South Africans are infected with the CCP virus (COVID-19) during the current fourth wave, they are 80% less likely to be hospitalized if they have the Omicron variant compared to other strains, according to a study released by the National Institute for Communicable Diseases.

Once hospitalized, the risk of severe disease is no different from other variants, according to authors led by scientists Nicole Walter and Cheryl Cohen.

Compared to Delta infections in South Africa between April and November, Omicron infections have a 70% lower risk of severe disease. The data for the Omicron variant was collected over the two months leading up to November.

Since being identified by South African scientists on November 25, the Omicron subvariant has generated record numbers of cases across South Africa. In this most economically developed country in Africa, about 44% of the adult population has been fully vaccinated in seven months.

The data, submitted to the preprint media MedRxiv, adjusted for various confounding factors that could influence the results, such as age, sex, and whether the case was a known reinfection. For severity after hospitalization, they also adjusted for the presence of other illnesses and vaccination status.

It was also shown that Omicron patients may have higher viral loads.

Paul Hunter, a professor of medicine at the University of East Anglia in the UK, said the study is "important" but that its results might be biased by the passage of time because it uses so-called historical controls when comparing to infections from the Delta variant between April and November.

"Even though Omicron cases are less likely to be taken to the hospital than Delta cases, we do not know if this is due to an inherent difference in pathogenicity or because the population has higher immunity in November compared to earlier times," Professor Hunter said.

The authors point out the same limitations.

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