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The wave of Omicron appears to be milder according to preliminary studies published in the UK and South Africa.
Early evidence suggests fewer people are needing hospital treatment than with other variants – with estimates ranging from a 30% to a 70% reduction.
But the concern remains that even if Omicron is milder, the sheer number of cases could overwhelm hospitals.
More than 100,000 cases have been reported in the UK in a single day for the first time.
A deeper understanding of the severity of Omicron will help countries decide how to respond to the virus.
The study in Scotland has been tracking coronavirus and the number of people ending up in hospital.
It said that if Omicron behaved the same as Delta, they would expect around 47 people to have been admitted to hospital already. At the moment there are only 15.
The researchers said they were seeing a roughly two-thirds reduction in the number needing hospital care, but there were very few cases and few at-risk elderly people in the study.
Dr Jim McMenamin, the national Covid-19 incident director at Public Health Scotland, described it as a “qualified good news story”.
He said the data was “filling in a blank” about protection against hospitalisation, but cautioned it was “important we don’t get ahead of ourselves”.
The Omicron variant is spreading incredibly quickly and a high number of cases could wipe out any benefit of it being milder.
Prof Mark Woolhouse, from the University of Edinburgh, said: “An individual infection could be relatively mild for the vast majority of people, but the potential for all these infections to come at once and put serious strain on the NHS remains.”
Meanwhile, another study in South Africa also points to the Omicron wave being milder.
It showed people were 70-80% less likely to need hospital treatment, depending on whether Omicron is compared to previous waves, or other variants currently circulating.
However, it suggested there was no difference in outcomes for the few patients that ended up in hospital with Omicron.
“Compellingly, together our data really suggest a positive story of a reduced severity of Omicron compared to other variants,” said Prof Cheryl Cohen of the National Institute for Communicable Diseases, in South Africa.
Why milder?
The reduction in severity is thought to be a combination of the fundamental properties of the Omicron variant as well as high levels of immunity from vaccinations and previous infections.
An analysis of Omicron by Imperial College London suggests Omicron’s mutations have made it a milder virus than Delta.
The researchers said the chances of turning up at A&E would be 11% lower with Omicron than Delta if you had no prior immunity.
However, that now applies to relatively few people due to high levels of vaccination and infection.
The same analysis said that accounting for immunity in the population meant a 25% to 30% lower risk of visiting A&E with Omicron and around a 40% reduction in needing to stay in hospital for more than a day.
Prof Neil Ferguson, one of the researchers, said: “It is clearly good news, to a degree.”
However, he warned the reduction is “not sufficient to dramatically change the modelling” and the speed that Omicron is spreading meant “there’s the potential of still getting hospitalisations in numbers that could put the NHS in a difficult position”.
Laboratories studies have suggested potential reasons Omicron could be milder.
The University of Hong Kong found Omicron was better at infecting the airways, but worse at getting into the deep tissues of the lungs, where it can do more damage.
The University of Cambridge found the variant was not as good at fusing lung cells together, which happens in the lungs of people who become severely ill.
The UK Health Security Agency is expected to publish early real-world data on Omicron soon, which could give further indications of the variant’s severity.
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