South Africa has reported data on Covid cases driven by the Omicron variant that appears to give added impetus to claims the country is experiencing a lower severity of disease.
“In South Africa, this is the epidemiology: Omicron is behaving in a way that is less severe,” said Prof Cheryl Cohen of the country’s National Institute for Communicable Diseases (NICD), one of the authors of the study.
“Compellingly, together our data really suggest a positive story of a reduced severity of Omicron compared to other variants,” she said during a news conference by a group of NICD scientists on Wednesday.
Scientists, however, cautioned that the reasons less severe cases were being seen was not fully understood and that South Africa’s experience – with a young population – might not translate into how other countries experience Omicron.
In South Africa the median age is 27.6 years in comparison with the UK where it is 40.5 years and Italy – hard hit by the first wave of the pandemic – where it is 47.3.
Omicron cases around the world
“The lower risk or lower proportions of severe disease we’re seeing in the fourth wave could be due to a number of factors including the level of prior immunity from people who’ve already gotten vaccinated or had natural infection, or it could also be due to the intrinsic virulence of Omicron,” said Dr Waasila Jassat, of the NICD.
“But we need more studies to be able to unpack these things,” she said.
The question of immunity from vaccination or prior infection was flagged as a potential contributory factor last week by researchers at the University of Cape Town in a symposium of the World Health Organization after work that suggested that some of the body’s defences against Omicron – in particular so-called killer T-cells – may remain robust.
While evidence from South Africa about the virulence of the Omicron variant is being studied around the world – including in the UK – the NICD’s Michelle Groome warned that the South African data could not necessarily be extrapolated to other countries with different population profiles.
Much of the interest in the past fortnight in South Africa’s experience of Omicron, where the variant was first identified, has been driven by reports from public and private hospitals and health providers that has suggested lower levels of hospitalisation, admission to ICUs and use of oxygen for patients.
Against the more optimistic claims that the fourth wave of Covid in South Africa might be less severe, in the past week there has been an uptick, so far small, in hospitalisations and deaths in South Africa’s hospitals.
The claims about virulence came as some South African experts were claiming a “sustained drop” of new Covid cases. From nearly 27,000 new cases nationwide on Thursday, the numbers dropped to about 15,424 on Tuesday, although those claims may still be premature and also influenced by other statistical factors.
Marta Nunes, a senior researcher at the vaccines and infectious diseases analytics department of the University of Witwatersrand, told the Associated Press: “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.”
“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 was “not unexpected in epidemiology that a very steep increase, like what we saw in November, is followed by a steep decrease”.