A new strain of the coronavirus is spreading rapidly in London and south-east England.
Health secretary Matt Hancock has warned the situation is “getting out of control”, with officials reporting the strain may be up to 70% more transmissible.
In the affected parts of the country, more than 400 people in every 100,000 have tested positive for the infection in the past seven days up to 15 December – with an 175% increase in the Essex borough Thurrock.
This prompted officials to introduce tier 4 regulations, which prohibit indoor mixing of different households for the foreseeable future, including over Christmas.
For the rest of the country, the relaxed rules have been cut from 23 to 27 December, to just Christmas Day.
While officials have stressed it is unclear if the new strain causes more severe disease or is immune to the much-awaited vaccines, one expert warned “we are on a precipice”.
What does the new strain mean for a vaccine?
An effective vaccine has long been hailed as a route back to life as we once knew it.
While hundreds are under development worldwide, the Pfizer-BioNTech jab is the only one approved in the UK to date, with 350,000 vulnerable people already receiving its first dose.
Seventeen mutations have been recorded that “change the protein sequence of one of the viral genes”, according to Dr Jeffrey Barrett from Wellcome Sanger Institute.
“There are also a couple of synonymous (sometimes called ‘silent’) mutations that don’t have any function, but crop up and come along for the ride,” he added.
The 17 mutations affect the coronavirus’ spike protein, which it uses to enter cells. The spike protein is also a target for many vaccines.
Scientists are racing to uncover if the Pfizer-BioNTechn jab – as well as those in a late stage of development – are still effective, with results expected in the coming weeks.
While no one can say for sure ahead of the data, some are optimistic.
Speaking of the rising cases around London, Professor Daniel Altmann from Imperial College London said: “As far as I can see this greatly strengthens the case for all to get vaccinated as soon as possible.
“The vaccines induce neutralising antibodies [immune-fighting proteins] to several parts of spike and most of these would be unchanged by the mutations; so the vaccines will still work.”
Several experts have warned the highly-transmissible strain means more people must be immunised to achieve herd immunity; when a sufficient number are protected to prevent the infection taking hold in the community.
“The vaccines should still be as effective [at] reducing the risk of severe disease [and] death in people vaccinated,” said Dr Michael Head from the University of Southampton.
“The increased transmissibility does mean even with some benefit from vaccine on reducing transmissibility, the vaccination programme is even less likely to protect those people who choose not to be vaccinated.”
Watch: ‘We should be very concerned’ over new coronavirus strain
Is the new strain more dangerous?
The fact the coronavirus mutated is entirely expected.
The coronavirus is an RNA virus, which mutate almost constantly. In simple terms, RNA is a precursor to the more well known DNA.
Most mutations are neutral, while others can be advantageous or detrimental to the virus.
Neutral and advantageous mutations can become more common as they pass to descendant viruses. Detrimental mutations tend not to “stick”; think survival of the fittest.
“It has been suggested changes to the virus surface spikes may allow it to bind onto cells more easily,” said Dr Head.
“However there isn’t evidence yet the new virus is more or less dangerous in terms of its ability to cause disease.
“Sadly, we will have to wait and see if hospitalisations and deaths increase or decrease to find out.”
Do experts support tougher restrictions?
While missing out on festive get-togethers will undoubtedly have caused disappointment, experts have long warned in-person celebrations could have “dire consequences”.
“The escalating case numbers mean dramatic interventions are essential, so the new announcements are important and will help to provide some element of control on the national landscape,” said Dr Head.
With many questions surrounding the new strain, tougher regulations may allow scientists to play catch up.
“The greater curbs on social interactions - even at Christmas - allow time for scientists to learn and characterise this new strain, and in doing so, prevent the repeat of mistakes that were made in the earlier stages of the pandemic,” said Dr James Gill from the Warwick Medical School.
“To be very clear, delaying introduction of new restrictions whilst we gather further data on this new strain will cost lives.”
Dr Shaun Fitzgerald from the University of Cambridge added: “The situation at present is extremely concerning and we are on a precipice.
“That’s why hard decisions about Christmas have to be made.”
What could the new strain mean for future restrictions?
Early analyses suggests the new strain has increased the reproduction number, or R, by 0.4, according to the government.
R is the number of people a person with the coronavirus is expected to pass the infection on to. If more than one, an outbreak grows. The latest estimate puts R at 1.1 to 1.2 nationwide.
“To me, these reports on the transmissibility of the new strain are even more depressing than I had anticipated,” said Dr Head.
“An increase in R of 0.4 or greater is extremely bad news.
“During the national lockdown in November the best we could achieve was an R value of somewhere between 0.8 and 1 around the UK.
“What this means is even if we went back to the national lockdown it would still not be enough to bring the R value down to less than 1.
“It is even uncertain whether if we went back to the lockdown of March and April we would bring the R value down to less than 1.
“So, perhaps, all we can now hope for is the epidemic increases less rapidly with the measures that the PM announced today.”
Professor Edmunds added: “It looks like this virus is significantly more infectious than the previous strains.
“This means to control it we are going to have to put in place much more restrictive measures.
“I am sorry to say it looks like there are tough times ahead, but the faster and more decisively we act the quicker we can begin to control this new virus.”
Could the strain be spreading elsewhere?
The new strain appears to be concentrated in London and its surrounding areas.
With footage of people fleeing the capital ahead of the tier 4 regulations, many experts are pessimistic it is just a matter of time before the strain is reported elsewhere.
“It is inevitable this new variant will spread throughout the UK and we can expect to see increased transmission rates in all regions and devolved administrations over coming weeks,” said Dr Head.
“The appearance of such an infectious variant of the virus at this time of year represents a perfect storm for the epidemic and is desperately bad news for attempts to control the epidemic.”
Italy and Australia have both reported cases of the new strain. It is also expected to appear in other nations, despite Canada and several European countries banning UK arrivals.
“There is no part of the UK and no country globally that should not be concerned,” said Dr Jeremy Farrar from the Wellcome Institute.
“As in the UK, in many countries the situation is very fragile.”
Watch: New coronavirus strain ‘out of control’, says Hancock