Editor's note, 19 December 2020: This article was updated with the latest information.
The new SARS-CoV-2 virus variant is spreading so rapidly that Prime Minister Boris Johnson announced a new Tier 4 for London, and parts of the South East and East of England that are currently in Tier 3.
Mr Johnson told a Downing Street briefing: "The new variant could increase the R by 0.4 or more, and although there's considerable uncertainty, it may be up to 70% more transmissible than the old variant, the original version of the disease."
England's Tier 4 is the equivalent of the old national lockdown restrictions and begins tomorrow.
It prevents Christmas relaxation for gatherings in Tier 4, aside from support bubbles.
Non-essential shops, gyms, and hairdressers will also close. People shouldn't enter or leave Tier 4.
In the rest of England, special Christmas measures are reduced to one day down from the previous 5.
Cancelling Christmas
Mr Johnson had previously said it would be "inhuman" to cancel Christmas.
"When the science changes, we must change our response," Mr Johnson said. "When the virus changes its method of attack, we must change our method of defence. And as your Prime Minister I sincerely believe there is no alternative open to me."
He added: "We're sacrificing the chance to see our loved ones this Christmas so we have a better chance of protecting their lives so that we can see them at future Christmases."
He denied he'd been slow to react to rising cases and evidence around the virus variant.
Rest of the UK
The PM's announcement for England followed calls with the cabinet, and with the leaders of Scotland, Wales, and Northern Ireland.
Wales has brought forward its planned national lockdown to start at midnight with rules eased on Christmas Day. First Minister Mark Drakeford said: "The situation is incredibly serious. I cannot overstate this."
Seventeen new variant cases have already been identified in Scotland. First Minister Nicola Sturgeon said: "We do now face a very serious situation. It is, in fact, probably the most serious and potentially dangerous juncture we have faced since the start of the COVID pandemic in February, and March."
Although she said the situation in Scotland is not as severe as other parts of the UK, preventative measures were needed.
Restrictions will now only be lifted on Christmas day itself, and there's a ban on non-essential travel to and from the rest of the UK.
Level 4 measures will be applied to all of mainland Scotland for 3 weeks from Boxing Day.
Ms Sturgeon said making the announcement about Christmas made her want to cry.
New Variant
The variant was identified through Public Health England genomic surveillance. Chief Medical Adviser Professor Chris Whitty issued a statement saying: "As a result of the rapid spread of the new variant, preliminary modelling data and rapidly rising incidence rates in the South East, the New and Emerging Respiratory Virus Threats Advisory Group (NERVTAG) now consider that the new strain can spread more quickly.
"We have alerted the World Health Organisation and are continuing to analyse the available data to improve our understanding.
"There is no current evidence to suggest the new strain causes a higher mortality rate or that it affects vaccines and treatments although urgent work is underway to confirm this."
He told the news briefing: "In the South East, 43% of the virus is now this new variant, in Eastern England it's 59%, and in London 62%."
Rates of hospitalisation were higher where the new variant was more prevalent.
'Cause for Concern'
Chief Scientific Adviser Sir Patrick Vallance said: "The new variant contains 23 different changes, many of them associated with changes in the protein that the virus makes. This is an unusually large number of variants. It's also got variants in areas of the virus that are known to be associated with how the virus binds to cells and enters cells. So there are some changes, which cause concern in terms of how the virus looks."
He added: "This virus transmits and spreads fast."
The variant may have originated in the UK, Sir Patrick said: "There's a large outbreak in the UK, it may have started here, we don't know for sure."
Earlier, SAGE member, and Director of the Wellcome Trust, Sir Jeremy Farrar tweeted: "The new strain of COVID-19 is worrying & real cause for concern & extra caution. Research is ongoing to understand more, but acting urgently now is critical. There is no part of the UK & globally that should not be concerned. As in many countries, the situation is fragile."
Dr Samantha Batt-Rawden, president of Doctors’ Association UK and a senior intensive care registrar in the South East of England commented: "We realise how disappointing the new restrictions will be for many today, especially those in Tier 4 areas. However, doctors across the UK, but especially those in the South East are telling us that the surge in cases is already putting hospitals and critical care units under enormous strain."
Vaccines
Mr Johnson said 350,000 people across the UK have now had the first dose of the Pfizer/BioNTech vaccine.
Yesterday, the US FDA granted emergency use of Moderna's messenger RNA COVID-19 vaccine, the country's second after the Pfizer/BioNTech product.
The Moderna vaccine, and the Oxford/AstraZeneca jab, are still being assessed by the UK's MHRA.
Daily Data
In today's daily data another 27,052 UK positive tests were reported and 534 deaths.
The total number of deaths within 28 days of a positive test now stands at 67,075.
There are 18,771 COVID-19 patients in hospital and 1364 ventilator beds are in use.
See more global coronavirus updates in Medscape’s Coronavirus Resource Centre.
