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 cases in Manchester, and three other scattered cases.
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".
There are now four "variants of concern" of the virus that causes COVID-19, identified by government advisors.
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.
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