The Omicron variant of Covid-19 is less likely to cause severe disease than the Delta variant, according to two studies published yesterday that offer early support for Boris Johnson’s decision to pause further restrictions.
The risk of requiring an overnight stay in hospital was reduced by at least 40 per cent for people with Omicron compared with Delta.
Johnson, who has been briefed on the latest data, has decided to hold off announcing further restrictions in England, in contrast to Wales and Northern Ireland, which followed Scotland by tightening rules yesterday. Senior government sources said that the decision would be reviewed after Boxing Day.
The studies, described as “good news” by health officials, came as the UK reported more than 100,000 Covid cases on a single day for the first time.
Ministers are also hopeful about two new antiviral drugs that officials believe will be “vital tools” in the battle to keep people who catch the virus out of hospital. A deal for 4.25 million courses was announced yesterday.
Studies comparing patients with Delta and Omicron in England and Scotland showed an encouraging pattern of lower severity with the newer variant.
Researchers led by Professor Neil Ferguson at Imperial College London calculated a “moderate reduction” in risk from Omicron.
They found that, compared with Delta cases, Omicron cases were between 15 and 20 per cent less likely to need to go to A&E and 40 to 45 per cent less likely to be admitted to hospital for a night or more.
However, the lower efficacy of the vaccine against Omicron may offset the reduced severity of the virus, they warned. There is still a concern that even if Omicron is milder in general, a large number of cases will result in severe pressure on the NHS.
Ferguson, whose modelling guided the decision to go into lockdown in March last year, said: “Given the high transmissibility of the Omicron virus, there remains the potential for health services to face increasing demand if Omicron cases continue to grow at the rate that has been seen in recent weeks.”
The research looked at 56,000 cases of Omicron in England from December 1 to 14 and 269,000 cases of Delta. It also found that prior infection appeared protective against hospital admission with Omicron. There was not enough data to calculate any reduction in intensive care admissions or deaths for the new variant.
Research among Scottish patients found that people who tested positive for Omicron were about 64 per cent less likely to be admitted to hospital than those with the Delta variant. The level of Omicron hospital admissions had been “much lower than we expected”, Professor Chris Robertson, of the University of Strathclyde, said.
The study looked at nearly 127,000 Delta patients and nearly 24,000 with Omicron. The number of hospital admissions was small — 967 with Delta and 18 with Omicron.
Dr Jim McMenamin, the Covid-19 incident director at Public Health Scotland, said the results were “a qualified good news story”. There was still a risk, he stressed, that a surge in cases could overwhelm the NHS.
Professor James Naismith, director of the Rosalind Franklin Institute, who was not involved in the research, agreed that the findings were positive.
“The two-thirds reduction in hospitalisation of double vaccinated young people compared to Delta indicates that Omicron will be milder for more people,” he said.
However, the research also showed that Omicron can cause severe illness in people who are double-jabbed. “Thus if Omicron continues to double every few days, it could generate many more hospitalisations than Delta from the double vaccinated population,” Naismith said. Both studies are yet to be peer reviewed.
Senior government figures said the research showed that the booster campaign was “more important than ever” and could make a critical difference to the need for further social restrictions.
A Downing Street source said the data was still very uncertain and the prime minister wanted further information before making any changes to rules in England that would have to be approved by MPs and could potentially trigger another backbench revolt.
Another source said the latest studies provided cause for optimism that restrictions could be avoided, despite record Covid-19 cases.