It will be weeks before we know just how worried we should be about Omicron — but the first indications seem hopeful. The epicentre of the first recorded outbreak has been the subject of a study that suggests that it may be milder than Delta. Early data from 166 patients in the Tshwane district comes with the usual caveats, especially that very little Omicron has been found among South African over-65s. But the study nonetheless has two weeks of hospitalised Omicron patients to analyse — more than any other country. Here are the main indications so far:

• Fewer people hospitalised with Omicron have ended up in intensive care: 8 per cent, compared to 25 per cent for Delta.
• Fewer patients need oxygen: only about a third. A big change, the study says, because until now pretty much every Covid patient has needed oxygen.
• Most Omicron patients were not admitted for Covid: they registered due to hospital policy of testing everyone admitted.
• Vaccines may explain the younger profile of Covid patients: 57 per cent of over-50s have been vaccinated in the Tshwane province ‘compared to 34 per cent in the 18-to-49-year group’.
• Omicron patients are out of hospital sooner: 2.8 days ‘compared to an average length of stay of 8.5 days for the past 18 months’.

The report says that all this ‘constitutes a very different picture compared to the beginning of previous waves’. While we don’t know that every recent case in South Africa is Omicron, most of the Covid that has been sequenced has been the new variant. It is tempting to conclude that Omicron is bypassing vaccines if it has become dominant so quickly, but South Africa doesn’t have nearly the same level of vaccination as Britain — only 24 per cent have had two doses, compared to 88 per cent here.

The UK’s high vaccination rates put us in good stead, but what about reinfection? A British government-funded study in South Africa claimed that Omicron had the potential to reinfect people who’ve already had Covid. This would be new, as there has yet to be a variant that can do this to any significant extent. The data suggests that Omicron could be 2.6 times more likely than Delta to cause reinfection. Public Health England estimated that 1.2 per cent of Delta cases were people having had Covid twice, so if the South African figure is correct, we should expect about 3.1 per cent of Omicron cases to be among people who have already had Covid. A tangible rise, but not a catastrophe.

The biggest threat this winter will probably come from how transmissible Omicron is. Angelique Coetzee, chair of the South African Medical Association, told the BBC that the R number (the average number of people someone with Covid will give the virus to) was ‘about 6.3’ (Delta’s is just above 5). The original Wuhan strain was 2.8, so we could be looking at a variant more than twice as transmissible as the one that started the pandemic.

As Robert Peston writes, Omicron is no doubt spreading more than official case numbers suggest (246 cases were reported in the UK yesterday). But no one is suggesting the government’s numbers are exact: what they will tell us over the next few weeks is the rate at which Omicron is increasing. On this, early figures suggest a case-doubling time of three days (Delta is estimated to be 4.6 days). So there is reason to believe that Omicron is more contagious than any previous strain.

If Omicron becomes the dominant variant, it will do so in the new year. It seems likely that any pressure on the NHS would come from Omicron’s transmissibility — more people being infected at any one time — not from a nastier illness. We are still waiting for real-world data on how much it blunts the vaccines — but if it does, for most people it will be a reduction from three doses, not two (Pfizer said its booster increased protection by 96 per cent). If the early data from South Africa suggests Covid could be milder in a relatively unvaccinated population, there is reason to hope that a population with 93 per cent antibodies, such as the UK, could fare better.