Some research appears to show E484K may help the virus evade parts of the immune system called antibodies.
But early results from Moderna suggest its vaccine is still effective against variants with this mutation - although the body's immune response may not be as strong or prolonged.
Public Health England is investigating cases of coronavirus with 'worrying' new genetic changes that have been found in some regions of the UK.
Tests show they have a mutation, called E484K, that is already seen in the South Africa variant.
Although this change may reduce vaccine effectiveness, the current ones in use should still work, say experts.
There have been 11 cases in Bristol and a cluster of 32 cases in Liverpool.
Urgent testing for the South Africa variant is already starting in parts of England and could be rolled out to other areas seeing different variants with the same E484K mutation.
Scientists working with Public Health England found a small number of cases of the UK 'Kent' variant with the E484K mutation - it was seen in 11 out of 214,159 samples that they tested, and predominantly from the South West of England.
It is likely there may be more cases that haven't yet been found. The Liverpool area has seen 32 cases of original coronavirus that have the E484K mutation too.