The highly contagious Omicron strain of coronavirus that is driving record-high infections also appears to be a less severe form of the disease.
The UK Health Security Agency (UKHSA) said patients were between 31-45 per cent less likely to need to go to hospital emergency wards and between 50-70 per cent less likely to be admitted to hospital for treatment.
Omicron is behind the wave of Covid-19 hitting the UK as it threatens to become the dominant strain in Germany, France and elsewhere.
Health Secretary Sajid Javid welcomed the preliminary findings and stressed the key weapon in the government’s arsenal was delivering booster shots to as many people as possible.
“This new UKHSA data on Omicron is promising — while two doses of the vaccine aren't enough, we know boosters offer significant protection against the variant and early evidence suggests this strain may be less severe than Delta,” he said.
“However, cases of the variant continue to rise at an extraordinary rate — already surpassing the record daily number in the pandemic.”
Other studies have reported similar findings.
Omicron is associated with a two-thirds reduction in the risk of needing hospital treatment compared with the Delta variant, researchers in Scotland found. But it is 10 times more likely than Delta to infect people who had previously contracted Covid-19.
In South Africa, people contracting Covid-19 are 80 per cent less likely to need hospital treatment if they catch the new variant, compared with other strains.
Omicron infections are also associated with a 70 per cent lower risk of severe disease than Delta, the study from the South African National Institute for Communicable Diseases showed.
The findings will lead to hopes that the chances of further restrictions being imposed are reduced.
Mr Javid said there will be no further announcements on restrictions in England before Christmas.
“We are not planning any further announcements this week,” he said.
“Despite the caution that we are all taking, people should enjoy their Christmases with their families and their friends — of course, remain cautious.
“We will keep the situation under review. We are learning more all the time as we have done from this new data.
“We will keep analysing that data and if we need to do anything more, we will, but nothing more is going to happen before Christmas.”
The UK has embarked on a booster campaign, with more than 30 million extra doses of Covid-19 vaccine issued, approaching one million a day this week.
On Thursday, British pharmaceutical company AstraZeneca said that a third, or booster, dose of its Covid-19 vaccine “significantly” lifted antibody levels against the Omicron strain in a laboratory study.
“The third dose booster vaccination neutralised the Omicron variant to levels that were broadly similar to those observed … after the second dose against the Delta variant,” the company said.
In a preprint study, scientists in the Scotland-wide Early Pandemic Evaluation and Enhanced Surveillance of Covid-19 suggested those infected with Omicron were less likely to end up in hospital.
But the study said that more data was needed before definite conclusions could be drawn.
Jim McMenamin, the national Covid-19 incident director for Public Health Scotland, called the findings “qualified good news”, but said it was “important we don't get ahead of ourselves”.
“The potentially serious impact of Omicron on a population cannot be underestimated,” Dr McMenamin said.
“And a smaller proportion of a much greater number of cases that might ultimately require treatment can still mean a substantial number of people may experience severe Covid infections that could lead to potential hospitalisation.”
Authors of the paper, which has yet to be reviewed by peers, said if the Omicron coronavirus had been like the Delta variant in Scotland, they would have expected to about 47 people to be in hospital with the virus. But so far, there are only 15.
Imperial College London researchers said the risk of any visit to hospital with Omicron was between 20 per cent and 25 per cent lower than with Delta.
“Overall, we find evidence of a reduction in the risk of hospitalisation for Omicron relative to Delta infections, averaging over all cases in the study period,” they said.
The study analysed data from PCR-test confirmed cases in England between December 1 and 14.
The UKHSA is expected to release more data on Omicron on Thursday.
Despite the studies suggesting Omicron may result in milder infection compared with the Delta variant, there are still fears the UK's National Health Service could buckle under the wave because it is already under increasing strain.
Patricia Marquis, regional director at the Royal College of Nursing, said NHS staff were exhausted and were carrying workloads they would not have in normal times.
“What we’ve seen is nurses being physically and mentally exhausted,” she told Sky News. “They’re being redeployed, they’re doing things that they wouldn’t normally be doing. People are trying to cover the work of one, two, three, four colleagues who might be missing.”
Paul Elliott, chairman of epidemiology at Imperial College London, said a recent government-backed React-1 study conducted at the institution showed the infection rate among children aged 12 to 17 had halved compared with a previous study weeks earlier.
“So, we do see the real benefits of the vaccination programme in those older schoolchildren,” he told Sky News.
In Britain, vaccines are available for those over the age of 12
Prof Elliott said a “good proportion” of children over 12 who took part in the study had been vaccinated against Covid-19 and this age group reported fewer cases than children in primary school.
“Very interesting, what we saw from our previous survey which ended on November 5 to the current survey, which was between November 23 and December 15, we saw a drop by about half in the infection rate in the older schoolchildren,” he added.
“But the youngest children that you’re talking about, their prevalence remained about the same, about 4-5 per cent.
“So, we do see the real benefits of the vaccination programme in those older schoolchildren coming through in the data that we’re collecting.”
Prime Minister Boris Johnson has urged people to “take extra special care to protect yourselves and your families against Covid” over the Christmas period.
“The Omicron variant continues to surge across the country faster than anything we have seen before,” Mr Johnson said in an article for The Sun.
“So, please keep following the guidance, remembering to wear a mask when needed, open the windows for ventilation and take a test before visiting your nearest and dearest, particularly if they are elderly or vulnerable.”
In a video message posted on Twitter, the prime minster thanked everyone involved in efforts to send Covid-19 tests to people across the country. He said in the next month, up to 200 million lateral flow tests were due to be distributed by mail, helping ministers to keep track of cases.
Azra Ghani, head of infectious disease at Imperial College London, who took part in the study, said hospital admission figures for Omicron could go up if the variant became more prominent in older age groups.
“I think all of these studies are pointing at a sort of very similar picture but also pointing out that the context does matter,” she told the BBC Radio 4’s Today programme.
“So, we know, for example, in South Africa, we have a younger population but also very high previous levels of infection with the Delta variant wave there. So, all of these patterns make a difference in terms of the likelihood of seeing the population needing to attend hospital.
“We still have only a very small number of cases attending hospital so far and we need to bear in mind that Omicron has really been circulating in a younger population.
“The big concern is that over this Christmas period, there’s going to be a lot more intergenerational mixing and we don’t really know yet what that severity pattern might look like in the oldest age groups.”
Andrew Hayward, director of the UCL Institute of Epidemiology and Health Care and a member of Nervtag, said that the two new British studies of Omicron and emerging South African data showed “we can reasonably say, among mainly young adults who normally have mild disease anyway, that the severity is reduced compared to Delta".
“And that’s reduced maybe nearly a half in terms of likelihood of being admitted to hospital and maybe by about a quarter in terms of the chance of going to accident and emergency,” he told the BBC Radio 4’s Today programme.
“I think what we can’t necessarily extrapolate to what level of reduction in severity we might see in elderly people and we also know that in elderly people the risk of severe disease throughout the pandemic has always been massively high.”