The Government has announced new Covid-19 restrictions for England amid concern cases of the Omicron variant are doubling every two to three days.
Boris Johnson announced the triggering of further restrictions, including vaccine passports for large venues and the reintroduction of working from home guidance, at a press conference on Wednesday evening.
It comes as leading epidemiologist Professor Neil Ferguson said a January lockdown could not be ruled out if hospitalisations spiral over Christmas and into the New Year.
Booster jab bookings opened for seven million people aged 40 and over on Wednesday and the wait for a third dose has been cut from six months to three amid growing concern about the new strain.
Professor Ferguson, a member of the Scientific Advisory Group for Emergencies (SAGE), said he would like to see ministers introduce stricter rules while the third jab campaign was ramped up.
“Case numbers are doubling at least every three days maybe even every two days at the moment,” he told BBC 4’s Today programme.
“To put that in context it is the same if not faster than we saw with the original strain of the virus in March of last year, so it is a concern.”
He added: “There is a rational just epidemiologically to try and slow this down to give us more time to principally get boosters into people’s arms, because we do think that people who are boosted will have the best level of protection, but also to buy us more time to better characterise the threat.
“If you imagine a Plan B plus with working from home might slow it down.”
The first lab tests on the Omicron strain in South Africa suggest it can partially evade the Pfizer jab.
However, existing vaccines should still protect people who contract the variant from severe Covid cases, a World Health Organization (WHO) official said on Wednesday.
The UK has some 440 infections identified so far - with over 100 of these discovered in London - and it is “likely to overtake” the dominant Delta variant before Christmas.
Professor Ferguson last year became known as “Professor Lockdown” when his work was key to introducing the first national lockdown in March 2020.
When asked if the UK could see similar restrictions imposed in January, he said “it is difficult to rule out anything” and “it might be possible at the current time”.
He added that Omicron had been “detected it almost every region” in the UK but cases are highest in London, as a the city which sees the largest number of visitors from abroad, and Scotland where the variant could have been “seeded” during the COP26 climate change summit last month.
The Government discussed introducing further restrictions on Tuesday. However sources said the Cabinet was split over Plan B proposals about vaccine passports, working from home advice and mandatory mask wearing in more settings before further data is revealed.
So far Downing Street has been promoting the scaling up of the rollout of booster jabs as the best protection from Omicron.
An outbreak of the variant at a Christmas party in Oslo, where up to 120 revellers were infected, has so far only caused mild disease, Norway’s state epidemiologist has said.
WHO has also said jabs should still protect people who contract the Omicron variant from extreme Covid.
Dr Mike Ryan, the WHO’s emergencies director, said on Wednesday: “We have highly effective vaccines that have proved effective against all the variants so far, in terms of severe disease and hospitalisation, and there’s no reason to expect that it wouldn’t be so for Omicron.”