The Kent Covid-19 variant that has been spreading around the UK appears to have mutated again, scientists say.
The mutation, called E484, has also appeared in South Africa and Brazil, raising concerns of its possible effect on current vaccines.
The news comes as the UK has implemented an urgent door to door testing process in eight areas of England to tackle the potential spread of new variants.
Current vaccines being administered should still work, experts said, although changes may affect vaccine effectiveness.
Important to follow lockdown rules
Dr Julian Tang, a virus expert at the University of Leicester, told the BBC that in order to prevent opportunities for Covid-19 to mutate further, it is important for people to follow lockdown rules.
Dr Tang said that allowing the spread of the virus to continue could allow a “melting pot” for different emerging variants.
Public Health England experts have found only 11 cases of the UK variant with the E484K mutation in the 214,159 samples they tested.
Scientists are continuing to check whether the new mutations will affect the design and effectiveness of existing Covid-19 vaccines.
Research has shown that the E484K mutation may help the virus evade part of the immune system called antibodies.
A preliminary study testing the Pfizer Covid vaccine against one of the mutations found in the South African variant appeared to show the jab is effective against the mutated virus.
Early results from Moderna suggest that its vaccine is also still effective against the South African variant, however immune response may not be as strong or prolonged.
The two new coronavirus vaccines from Novavax and Janssen appear to offer some protection, too. These vaccines are yet to be approved for use.