People who get infected with Omicron are 50 to 70 per cent less likely to be admitted to a hospital ward when compared with the Delta variant, analysis has said.
It also found a person who becomes infected with the variant is 31 to 45 per cent less likely to have to go to A&E.
The findings come from the first “real life” evidence gathered by the UK Health Security Agency into the threat posed by Omicron.
The fact that Omicron poses a lower threat in terms of the risk of hospitalisation ties in with two separate pieces of research published earlier on Thursday from Imperial College London and experts in Scotland.
But the revelation about the waning effectiveness of boosters after 10 weeks could cause concern particularly among older people, who were the first to receive a third jab and who are more at risk from Covid due to their age.
The UKHSA estimates that protection provided by the booster against symptomatic disease falls by about 15-25 per cent against Omicron, compared with their effectiveness against Delta.
It is not yet known whether protection provided by boosters against more serious disease or death also reduces as quickly, due to the small numbers of Omicron-infected people currently in hospitals.
However UKHSA scientists say it is likely that the booster will maintain a good level of protection against serious illness and have urged Britons to continue to come forward for a third jab.
Most people aged 65 and older will have received a booster eight to 10 weeks ago, with only a small number having had it earlier and thus being at greater risk.
The UKHSA said it was too early to say whether a fourth dose would now be needed to maintain protection and suggested that a new vaccine specially targeted at Omicron might be needed.
They said it would take two to three weeks before there was sufficient data from hospitals to indicate how well boosters were performing against the worst impacts of Omicron.
The UKHSA said despite the “encouraging” findings about the general risk from Omicron, “significant” numbers of people could still need hospital treatment in the next few weeks due to its high transmissibility.
By Monday December 20, 132 people with Omicron had been admitted to hospital – of which more than 30 were in London.
Analysis of the 132 Omicron hospital patients found 17 had received a booster vaccine, 74 had two doses and 27 were not vaccinated. The vaccination status was unknown for six people, while eight had received a single dose.
Most of the people hospitalised with Omicron were aged 20 to 40.
A total of 14 people are reported to have died within 28 days of an Omicron diagnosis, ranging from 52 to 96 years old.
The reduced risk of seeking hospital care or ending up on a ward was regardless of vaccination status or age. The estimate also excluded people who had previously had a confirmed Covid infection.
But the precise reduction in risk is said to be “highly uncertain” because of the small number of people being hospitalised to date.
The UKHSA said that 9.5 per cent of people catching Omicron had previously had Covid - a much higher reinfection rate than previously. But this is likely to be a substantial underestimate of how well Omicron evades immunity from prior infection.
Dr Jenny Harries, UKHSA chief executive said: “Our latest analysis shows an encouraging early signal that people who contract the Omicron variant may be at a relatively lower risk of hospitalisation than those who contract other variants. However, it should be noted both that this is early data and more research is required to confirm these findings.
“Cases are currently very high in the UK, and even a relatively low proportion requiring hospitalisation could result in a significant number of people becoming seriously ill. The best way that you can protect yourself is to come forward for your first two doses of vaccine, or your booster jab and do everything you can to stop onward transmission of the infection.”
Health and Social Care Secretary Sajid Javid said: “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.
“However, cases of the variant continue to rise at an extraordinary rate – already surpassing the record daily number in the pandemic. Hospital admissions are increasing, and we cannot risk the NHS being overwhelmed.
“This is early-stage analysis and we continue to monitor the data hour by hour. It is still too early to determine next steps, so please stay cautious this Christmas and get your booster as soon as possible to protect yourself and your loved ones.”