The Omicron variant could cause the UK’s biggest Covid wave yet which would overwhelm the NHS, Government advisors have warned.
A SAGE subgroup said it “can’t rule out” the drastic scenario if the B.1.1.529 strain has a major resistance to the vaccine.
The New and Emerging Respiratory Virus Threats Advisory Group (NERVTAG) said Omicron’s multiple mutations “are highly likely” to make antibodies from vaccination or previous infection less effective.
The experts said there was not yet direct experimental evidence of “immune escape”, but evidence so far was “highly suggestive” that it can infect previously infected or vaccinated people.
They added: “If introduced into the UK, B.1.1.529 would likely be capable of initiating a new wave of infections.
“We cannot exclude that this wave would be of a magnitude similar, or even larger, than previous waves.”
They went on: “Although data on disease severity associated with B.1.1.529 are not yet available, a large wave of infections will be accompanied by a wave of severe cases.
“The subgroup cannot rule out that this may be sufficient to overwhelm NHS capacity.”
The NERVTAG meeting was held on November 25, a day before Omicron was designated a variant of concern by the World Health Organisation.
Since then the government has extended boosters to all adults just three months after their second dose, and introduced mandatory mask-wearing and travel testing rules.
But leaked minutes of a main SAGE meeting - held on Monday - say it would be “valuable” to go further, forcing travellers to the UK to take a Covid test before they take their flight.
Currently travellers from non-red-list countries will only need to take a Day 2 test after arrival and isolate until it comes back negative.
The leaked SAGE minutes said this approach will “identify significantly fewer cases" than an additional test on either day five or day eight.
Labour have demanded the return of pre-departure tests while the Welsh and Scottish governments have called for tests on Day 8, and for travellers to isolate until then.
New Shadow Home Secretary Yvette Cooper said: “It is totally unacceptable that Ministers are failing to take action at the border when even their own advisors are telling them to introduce pre-departure tests.
“It cannot be right that people can travel to an airport, board a busy flight, queue at busy departure gates, and travel on trains and buses in the UK, all without having taken a test.
“The government must not repeat the mistakes it made earlier in the pandemic by being too slow to take action to prevent further cases of the Omicron variant entering the UK.”
It came as the leaked minutes of a main SAGE meeting said the Omicron variant could need “very stringent response measures” if it threatens the NHS.
Notes from a meeting on Monday, obtained by the BBC, say it is “highly likely” that the multiple-mutated strain can resist vaccine immunity “to some extent”, like the Delta variant already does.
The notes add: "Any significant reduction in protection against infection could still result in a very large wave of infections.
“This would in turn lead to a potentially high number of hospitalisations even with protection against severe disease being less affected." It comes after Boris Johnson last night insisted a Christmas lockdown was "extremely unlikely".
A government spokesman did not deny the minutes were genuine and warned: “We continue to monitor the situation closely and will not hesitate to take further action if necessary.”
Face mask laws and mandatory 10-day isolation for close contacts of suspected Omicron cases have been introduced for three weeks - and could be extended beyond December 20 - while scientists work out the risk.
Health Secretary Sajid Javid today said people “maybe” want to take a lateral flow test before going to Christmas parties.
But he rejected comments of government advisor Dr Jenny Harries who suggested people may want to cut down on socialising. Mr Javid agreed with Boris Johnson, saying there is no need to cancel plans.
And Mr Javid claimed the restrictions “might” be reviewed earlier than the planned three-week review date on December 20.
"We are confident that actually maybe within two weeks we will know a lot more about this. We may not even need to wait three weeks," he said.
A government spokesperson said: “As soon as we became aware of the Omicron variant we took rapid action to protect public health - including expanding the red list, introducing PCR testing for travellers, changing the rules on self-isolation for close contacts and mandating face coverings in shops and on public transport.
“On top of this we are speeding up our vaccination programme by offering all adults in England a booster jab by the end of January, halving the gap between second doses and boosters, and offering second jabs to 12-15 year olds, following advice from the JCVI."
