Johannesburg: A South African study offered Christmas glad tidings about the severity of Omicron and the trend of COVID-19 infections on Wednesday as the fast-spreading coronavirus variant forced countries across the world to impose new curbs.
The study by the National Institute for Communicable Diseases (NICD) suggested that those infected with Omicron were much less likely to end up in hospital than those with Delta.
COVID-19 cases also appear to have peaked in South Africa’s Gauteng province, which is its commercial hub and the region of the country where Omicron first emerged.
Omicron was first detected last month in southern Africa and Hong Kong. Preliminary data indicates it is more resistant to vaccines developed before it emerged.
South Africa’s NICD study, conducted with major universities, has not been peer-reviewed. It compared South African Omicron data from October and November with data about Delta between April and November.
The authors found that the risk of hospital admission was roughly 80% lower for those with Omicron, and that for those in hospital the risk of severe disease was roughly 30% lower.
“In South Africa, this is the epidemiology: Omicron is behaving in a way that is less severe,” said Professor Cheryl Cohen of the NICD, one of the authors.
“Compellingly, together our data really suggest a positive story of a reduced severity of Omicron compared to other variants.” Still, the authors included caveats and cautioned against jumping to conclusions, saying high population immunity was a likely factor. A study by Imperial College London last week found no sign Omicron was milder.
In the data that are being submitted to a preprint medical publication - MedRxiv - the authors adjusted for various confounding factors that could influence the results, including age, gender and whether the cases were known reinfections. For severity of disease after admission, they also adjusted for the presence of other illnesses and prior immunisation.
Sharp drop in cases
The study also showed that those with omicron may have higher viral loads. The study is “important,” though its use of so-called historic controls when comparing to the Delta infections between April and November means its outcome may be biased by time issues, said Paul Hunter, a professor of medicine at the UK’s University of East Anglia.
“So even though cases of Omicron were less likely to end up in hospital than cases of delta, it is not possible to say whether this is due to inherent differences in virulence or whether this is due to higher population immunity in November compared to earlier in the year,” Hunter said.
The authors flagged the same limitations.
South Africa has been at the forefront of the Omicron wave and the world is watching for any signs of how it may play out there to try to understand what may be in store.
After hitting a high of nearly 27,000 new cases nationwide on Thursday, the numbers dropped to about 15,424 on Tuesday. In Gauteng province — South Africa’s most populous with 16 million people, including the largest city, Johannesburg, and the capital, Pretoria — the decrease started earlier and has continued.
“The drop in new cases nationally combined with the sustained drop in new cases seen here in Gauteng province, which for weeks has been the centre of this wave, indicates that we are past the peak,” Marta Nunes, senior researcher at the Vaccines and Infectious Diseases Analytics department of the University of Witwatersrand, told The Associated Press.
“It was a short wave ... and the good news is that it was not very severe in terms of hospitalisations and deaths,’’ she said. It is “not unexpected in epidemiology that a very steep increase, like what we saw in November, is followed by a steep decrease.’’
Gauteng province saw its numbers start sharply rising in mid-November. Scientists doing genetic sequencing quickly identified the new, highly mutated omicron variant that was announced to the world on November 25.
Significantly more transmissible, Omicron quickly achieved dominance in South Africa. An estimated 90% of COVID-19 cases in Gauteng province since mid-November have been Omicron, according to tests.
