The true threat posed by the omicron coronavirus variant is unlikely to be determined until the turn of the new year, scientific advisers to the government have warned.
Experts from the Scientific Pandemic Influenza Group on Modelling (SPI-M) believe “the worse the problem is going to be, the earlier we will know” – but it’s expected to take a month before data indicates whether omicron will drive a surge in hospitalisations among the vaccinated.
More than 40 cases have now been detected in the UK, but analysis suggests the real figure may be much higher, amid concern that holes in the country’s Covid testing network could lead to an underreporting of omicron infections.
The World Health Organisation has said lab-based information on the transmissibility of the variant will be available “within days,” but this will not provide a full picture of how vaccine-acquired or natural immunity is diminished by omicron, or to what extent.
Members of SPI-M, a sub-committee of Sage, have said officials in the UK and beyond will likely know in a minimum of four weeks whether omicron, which has acquired a high number of concerning mutations, is bypassing pre-existing immunity in people and forcing them into hospital.
“If we don’t see a sharp rise in [omicron-positive] cases or hospitalisations in the next four to six weeks, then we can start to relax,” said Matt Keeling, a professor of mathematics and life sciences at the University of Warwick and SPI-M expert.
“However, we may realise that there are problems much sooner. We could start seeing dramatic rises in [omicron] cases within a week or two, although the knock-on effects on hospital admissions will take longer.”
Officials in South Africa have warned that the variant is already growing at an exponential rate in the country. It appears to be responsible for a rise in cases that is steeper and quicker than previous reported surges, though hospital admissions seem to be tracking previous climbs.
Covid cases in South Africa doubled between Tuesday and Wednesday of this week, rising from 4,373 to 8,561. However, it remains unclear how many of these new infections were caused by omicron.
Hospitalisations have also recently jumped in Gauteng province, the epicentre of South Africa’s omicron outbreak, but further data is needed to establish the age and vaccination status of those being admitted.
Professor Adrian Hill, one of the scientists behind the Oxford vaccine, said it would be “worrying” if there are “a lot of severe cases and hospitalisations amongst older people in southern Africa”. He added: “It hasn’t happened yet, but it hasn’t been long.”
The WHO said it has received reports of a range of cases “that go from mild disease all the way to severe disease”, while scientists from South Africa’s National Institute for Communicable Diseases (NICD) said they believed that reinfections from omicron “will be less severe”.
“That’s what we’re trying to prove and to monitor very carefully in South Africa. And the same would hold for those that are vaccinated,” said Anne von Gottberg, a microbiologist at the NICD.
Prof Hill said nervous scientific onlookers were not yet in a position to draw firm conclusions from the South African epidemiology. “But if in a month there’s no outbreak of lots of severe cases [driven by omicron],” he added, “I think we’ll be a lot more relaxed.”
SPI-M chair Graham Medley, a professor of infectious disease modelling at the London School of Hygiene & Tropical Medicine (LSHTM), said “to detect the impact of omicron on hospitalisations we will need several thousand infections, and hopefully it takes several weeks before we have them.”
He added: “The worse the problem is going to be, the earlier we will know.”
In England, there were an estimated 60 omicron cases by 28 November, according to analysis from Dr Nick Davies, an evolutionary biologist and epidemiologist at LSHTM. At the time, just a handful of people were confirmed to have been infected with the variant.
Dr Davies’ analysis also suggests that the number of Covid samples which are likely to be omicron has risen from around 0.1 to 0.3 per cent in recent days.
His findings come amid concern that between a third and a half of UK labs have the required technology to detect suspected omicron cases, meaning some infections may fly under the radar.
Dr Jenny Harries, chief executive of UK Health Security Agency, said on Thursday that officials are expecting to “find more cases over the coming days as we are seeing in other countries globally and as we increase case detection through focused contact tracing.”
Meanwhile, the European Union’s public health agency has said that omicron could be responsible for more than half of all Covid infections across the continent within a matter of months. It added that no cases of severe disease had yet been identified in the region.
Europe has so far recorded 79 cases of the Omicron variant first detected in southern Africa last month, according to European Centre for Disease Prevention and Control (ECDC).
The ECDC’s prediction is based on mathematical modelling which could lend weight to early estimates about the high transmissibility of omicron, suggesting it will go on to outcompete the globally dominant delta variant.