The Imperial team, led by Professor Neil Ferguson, said there was little evidence to suggest that omicron was milder, in contrast to mounting real-world and laboratory data showing the opposite.
Imperial’s own data, which looked at more than 200,000 cases between November 29 and December 11 also showed that the risk of needing hospital attention from omicron was 0.15 per cent compared to 0.66 per cent compared to delta – four times less.
Modelling behind Sajid Javid’s claim of 200,000 daily omicron infections ‘no longer valid’
Health officials admit it is now wrong to assume the doubling rate will remain constant, as new measures are slowing the spread of Covid-19
Modelling used to justify Sajid Javid’s claim that there were 200,000 omicron infections a day has been abandoned by health officials, who say it is "no longer valid" because of behavioural changes.
On Monday, the Health Secretary caused widespread confusion by announcing the figure without releasing the methodology behind the calculation.
The UK Health Security Agency (UKHSA) consistently warned this week that omicron infections were doubling every 1.9 days. But a methodology memo published quietly by the UKHSA on Thursday states it is now wrong to assume that the doubling rate will remain constant, and so should no longer be used.
A spokesman said the figure had given a “useful snapshot” to “emphasise the scale” at which omicron was spreading, but argued that increased mask wearing and working from home had altered the forecast. The UKHSA could not give an up-to-date estimate of infections.
It comes after a poll suggested that the public are tiring of restrictions. A YouGov survey for The Times newspaper found that a majority of people would not back pubs, restaurants or non-essential shops being shut or bans on meeting people from other households.
On Friday, new modelling by Imperial College was also criticised for failing to take into account real-world data from South Africa showing that omicron is causing fewer deaths and hospitalisations, and leading to shorter stays in hospital even for the oldest and most vulnerable.
Imperial warned that the risk of reinfection with the omicron variant is 5.4 times greater than that of the delta variant, although latest UKHSA real-world data suggests it is closer to three times.
The Imperial modelling suggests that in countries with high vaccination rates – such as Britain – an omicron wave could bring nearly 5,000 deaths a day – three times as many as the January wave. However, experts said this was unlikely.
Professor James Naismith, Director of the Rosalind Franklin Institute, said: “We can be confident that the double and especially triple vaccinated have protection against serious disease.
“As a result, the number of hospitalisations per 1000 infections of omicron will be significantly lower than the first wave. Better medicines and treatments will help too.”
The Imperial team, led by Professor Neil Ferguson, said there was little evidence to suggest that omicron was milder, in contrast to mounting real-world and laboratory data showing the opposite.
Imperial’s own data, which looked at more than 200,000 cases between November 29 and December 11 also showed that the risk of needing hospital attention from omicron was 0.15 per cent compared to 0.66 per cent compared to delta – four times less.
The Imperial model also states that a booster jab may only give 80 per cent protection against hospitalisation. However, models released last weekend by London School of Hygiene and Tropical Medicine state it could be anywhere between 84 per cent and 97 per cent.
‘Important not to over-interpret’
Commenting on the Imperial study, Dr Clive Dix, former chair of the UK Vaccine Taskforce, said: “It is important not to over-interpret this data. The conclusions made are based on making assumptions about omicron where we still don’t have sufficient data.
“For example, we have no data on the cellular immune response which is now probably driving the effectiveness of vaccines. This is a crucial missing assumption in the modelling.
“Some of their conclusions are different to the data emerging from South Africa in that the vaccines are holding up well against severe disease and death at present.
“There is a huge amount of uncertainty in these modelled estimates and we can only be confident about the impact of boosters against omicron when we have another month of real-world data on hospitalisation, ICU numbers and deaths.”
On Friday, health officials in South Africa confirmed that fewer people have died or required hospital treatment from omicron than in previous waves despite a record number of new infections.
Data from the city of Tshwane showed that the case fatality rate has plummeted for all age groups since the delta wave, even among the most elderly and vulnerable.
The death rate for over-80s is around 20 per cent compared to nearly 50 per cent in the delta wave. For 70 to 79-year-olds it has fallen from about 40 per cent to just 10 per cent.
‘Relatively small increases’
“The hospitalisations are not increasing at such a dramatic rate,” said Michelle Groome, the head of Public Health Surveillance at South Africa’s National Institute for Communicable Diseases (NICD).
“We are starting to see some increases, but relatively small increases in deaths.”
Leaked minutes of a Sage meeting reportedly said that "more stringent measures would need to be implemented very soon" to prevent hospital admissions peaking at more than 3,000 a day. They said that delaying measures until next year would "greatly reduce the effectiveness", BBC journalist Jim Reed said.
On Friday, the UK Government reported 93,045 new cases of Covid-19, the third day in a row that a record number of daily cases has been reached since the pandemic began.
Hospital admissions have also risen by eight per cent in a week, to 900, although the vast majority of these are caused by delta. Deaths are continuing to fall, with 111 reported on Thursday, down 4.5 per cent since last week.
Prof Polly Roy, professor of virology at the London School of Hygiene & Tropical Medicine, said: “There is a prevailing view that omicron represents a dramatically increased threat – but we don’t yet have all the evidence we need to know that.
“While continued spread of the virus does run the risk in reaching those who are vulnerable or unvaccinated, particularly in the winter months, the increased risk to the majority vaccinated population is probably marginal.
“While keeping up with your shots of the existing vaccine is good practice, lurching into precipitous social policies or change of vaccine are not.”
A Cobra meeting will be held over the weekend with the devolved administrations to discuss the response to the omicron variant, Mr Johnson said.
