A new coronavirus variant that may partially evade vaccine-triggered immunity and was first spotted in New York is already in Britain, health chiefs confirmed today.
And swabbing suggests the variant — dubbed B.1.526 — may have been lurking here for at least a month.
Scientists tracking the constantly-evolving virus say three cases of the mutant strain — which has caused havoc in New York — have been picked up in the UK.
Public Health England bosses claim the virus would have been spotted in travellers quarantining after flying into Britain. They did not deny it has already been detected three times in the UK.
The US is not on Number 10’s quarantine ‘red list’, with arrivals instead asked to self-isolate at home for ten days.
Many samples of B.1.526 detected in New York contained the troublesome E484K mutation, and a slew of other changes, which scientists say can make jabs slightly less effective.
This is because the mutation changes the shape of the virus’s outer spike protein — which it uses to invade cells — in a way that makes it difficult for the immune system to recognise.
But PHE says none of the three cases found in the UK contain the E484K mutation or the S677N mutation that was also spotted in New York.
The Government agency, which has yet to designate the strain as being a variant of concern, told MailOnline it was ‘monitoring the situation closely’.
A spokesperson added: ‘We are working with partners across the world to identify and mitigate the impact of variants as they emerge.’
It is not clear where Britain’s cases were found because PHE does not give away any further details.
But Pango lineages — which publishes figures on the number of variants identified by sequencing across the world — says Europe’s first case was detected on January 21, and the most recent was on February 27.
It is not clear when the first case was spotted in Britain.
Professor Lawrence Young, a virologist at the University of Warwick, said that any variant was a ’cause for concern’.
‘This find reinforces how important it is to keep an eye on things, we are not out of the woods yet,’ he told MailOnline.
‘It reinforces the fact that while things are looking really good right now there is no room for complacency.’
He added: ‘We need to keep Test and Trace going and stamp out what are inevitably going to be local outbreaks.’
New York’s public health officials have warned the strain shares key similarities with the worrisome South African variant, and can elude ‘some protection’ from jabs.
America’s top infectious diseases expert Dr Anthony Fauci says the strain can dodge ‘some of the protection of antibodies, as well as the vaccine’.
He also warned that it is spreading ‘pretty efficiently’ in the city.
The variant, which was first detected in November, was responsible for around 5 per cent of all positive tests in New York in late January, testing data suggested. Experts tracking the spread of the virus claimed the figure went up to roughly 27 per cent in mid-February.
Ministers launched door-to-door testing in dozens of postcodes when cases of the South African and Brazilian variants were found in the UK, in an attempt to stamp out all cases.
But they are yet to spark the same action for this strain, suggesting they are not as concerned by the variant.
Boris Johnson has set out four key criteria for lifting lockdown in the coming months, including that there no risky new variants emerge that could scupper the progress of the vaccine roll-out.
Three other European countries have reported cases of the B.1.526 variant, including Ireland (five), Croatia (three) and Germany (one), according to the database.
Britain has a superior sequencing capacity compared to other countries, which is now allowing it to check half of all virus cases detected for strains.
But its world-leading ability led to it becoming an international pariah last year after it raised the flag about the more infectious Kent variant, causing other countries to close their borders.
Experts say Britain was likely ‘caught out’ by its sequencing, and that it was possible the variant emerged elsewhere before being spotted in the UK.
The US has so far recorded as many as 2,565 cases of the New York variant.
The former head of the US medicines regulator, Dr Scott Gottlieb, warned yesterday it shared key mutations with the South African variant, which has been shown to re-infect people ‘in certain cases’.
The expert added on CBS: ‘What we don’t understand with B.1.526 is whether or not people are being re-infected with it and whether or not people who might have been vaccinated are now getting infected with it.’