A virus threats advisory group has classed a mutation of the Kent COVID strain found in Bristol as a "variant of concern".
NERVTAG - The New and Emerging Respiratory Virus Threats Advisory Group - fears the so-called Kent strain may be highly transmissible - but could also possibly interfere with the vaccine.
There have been 14 cases in Bristol, four in Manchester, and three other scattered cases.
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Meanwhile a mutation identified in Liverpool has been classed as a "variant under investigation".
So far Public Health England (PHE) has identified 76 cases of these two new variants.
Despite worries about the Kent strain "interfering" with the vaccine, the group does believe vaccinated people should still be protected against severe illness caused by it and health officials have also said they have "a high degree of confidence that the vaccines will work against variants".
But there is concern that the mutation - named E484K - could make the vaccine less effective at stopping the spread of the virus.
Sky's technology correspondent Rowland Manthorpe explained the mutation changes the shape of the "original" Kent variant, making it harder for the immune system to recognise and neutralise the virus, even if it has been shown what to do by the vaccine.
He said: "It has still about the same transmissibility, but it seems that this mutation might enable it to escape immunity to some extent, which means that it's possible it could evade the vaccine."
But, he stressed that the data was still "very sketchy" and at a "very early stage" and that lockdown remained the correct way of damping the emergence of new mutations.
There are now four "variants of concern" of the virus that causes COVID-19, identified by government advisors - three of these have been found in the UK.
These are the original Kent variant, the new Kent mutation, the South Africa strain and one from Brazil, which has not yet been found in the UK.
Officials are also tracking two "variants under investigation" - the Liverpool mutation and a further one from Brazil.
Test and Trace has identified 170 cases of the South Africa variant, including 18 cases unlinked to travel.
Dr Susan Hopkins, from PHE, told a briefing for journalists: "To date we have identified 170 cases and 18 of these are unlinked to travel, and that means that they neither travelled abroad themselves or a direct contact with an individual that has travelled," she said.
She added that "the best way to keep the South African variant down is to reduce all cases.
"If we keep R below one, then it is highly unlikely this will become an exponential event."
Over three nights Sky News will host a series of special programmes examining the UK's response to the pandemic.
Watch COVID Crisis: Learning the Lessons at 8pm on 9, 10 and 11 February
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2021-02-09 18:13:21Z
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