A South African study suggests that there is a lower risk of hospitalization and serious illness in people infected with the disease. Omicron variant of the coronavirus than those infected with Delta, although the authors affirm that part of this is probably due to the high immunity of the population.
Questions about the virulence of Omicron are at the center of scientific and political debate in many countries, as governments struggle to respond to the spread of the variant while researchers scramble to understand it.
The new study, which has not been peer-reviewed, attempted to assess the severity of the disease by comparing data on the omicron infections in October and November with data on delta infections between April and November, all of them in South Africa.
The analysis was carried out by a group of scientists from the National Institute of Communicable Diseases (NICD) and leading universities such as the University of the Witwatersrand and the University of KwaZulu-Natal.
They used data from four sources: national data from Covid-19 cases reported to the NICD, public sector laboratories, a major private sector laboratory, and genome data from clinical samples sent to the NICD from private and public diagnostic laboratories across the country.
The authors found that the risk of hospital admission was approximately 80% lower for those infected by Omicron compared to those in Delta, and that for those who were hospitalized the risk of serious illness was approximately 30% lower.
However, they did include several caveats and advised that no hasty conclusions should be drawn about the intrinsic characteristics of omicron.
“It is difficult to distinguish between the relative contribution of the high levels of prior immunity in the population and the lower intrinsic virulence to the lower severity of disease observed,” they wrote.
Paul Hunter, professor of medicine at the British University of East Anglia, described the South African study as important and said it was the first properly conducted study to appear in preprint form on the issue of severity Omicron versus Delta.
But Hunter said its main weakness was that it compared omicron data from one period to Delta data from a previous period.
“Thus, although omicron cases they were less likely to end up in hospital than those in Delta, it is not possible to say if this is due to inherent differences in virulence or if it is due to increased immunity in the population in November compared to the beginning of the year, “he said.
“To some extent, this does not matter to the patient, who only worries not to become seriously ill. But it is important to know this in order to better understand the likely pressures on health services.”