At a No 10 information convention, Mr Johnson mentioned he was taking the actions with a “heavy coronary heart”, however the scientific proof – suggesting the brand new pressure was as much as 70 per cent extra transmissible – had left him with no selection.
“With out motion the proof means that infections would soar, hospitals would change into overwhelmed and plenty of 1000’s extra would lose their lives,” he mentioned.
Sir Patrick instructed the briefing that present proof confirmed the variant “has a big, substantial enhance in transmissibility”.
“It’s additionally bought variants in areas of the virus which can be identified to be related to how the virus binds to cells and enters cells,” he mentioned
“So there are some modifications which trigger concern when it comes to how the virus seems to be.”
Sir Patrick set out how, in the midst of November, about 28 per cent of the instances in London and the South East, and barely decrease within the East of England, had been as a result of new variant.
“By the week commencing the ninth of December these figures had been a lot increased,” he mentioned.
“So in London, over 60 per cent of all of the instances had been the brand new variant.
“So what this tells us is that this new variant not solely strikes quick, it’s elevated when it comes to its capacity to transmit, however it’s turning into the dominant variant, it’s beating all of the others when it comes to transmission.
“So this virus transmits and spreads quick.”
Nonetheless, Sir Patrick mentioned there was “no proof” the variant induced extra extreme illness or elevated the chance of being admitted to hospital.
The “working assumption in the meanwhile from the entire scientists” can also be that vaccines ought to work in opposition to it, he added.
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“The large change subsequently isn’t illness progress, not immunity, however transmission – this virus spreads extra simply, and subsequently extra measures are wanted to maintain it underneath management.”
The Authorities’s chief medical officer, Professor Chris Whitty, instructed the press convention the tier system was holding instances in different elements of the nation however the brand new variant posed a threat to tiers.
“When you’ve got a low quantity of this variant, the speed of enhance is held by the tiers, however when you’ve got a really excessive fee of this variant, then it’s not held sufficiently by the tiers and it’s going up quickly,” he mentioned, including that folks mustn’t journey and threat spreading the variant across the nation.
He mentioned there was a threat of the variant “going out to different areas of the nation the place it presently isn’t an issue”.
Requested whether or not the present measures would work, he mentioned it was like “you had been biking up a steep hill and now you’ve bought the wind in opposition to you as effectively – you simply have to do this way more to truly hold going”.
However he mentioned measures equivalent to social distancing and limiting contact had been those to make use of.
Dr Jeffrey Barrett, director of the Covid Genomics Initiative on the Wellcome Sanger Institute, mentioned: “This new variant may be very regarding, and is in contrast to something we have now seen to date within the pandemic.
“The brand new restrictions introduced immediately are a wholly justified response to the quickly growing scenario.
“Detecting new variants like this is without doubt one of the key missions of the Covid-19 Genomics Consortium within the UK.
“The excessive stage of genomic surveillance we have now needed to date has helped detect and reply to this variant as rapidly as attainable. We are going to proceed to watch this and different variants within the weeks and months to return.”
Extra reporting by PA Media.