Experts in the UK say that now a new form of coronavirus that some call "Delta Plus" can spread more easily than the usual Delta.
The UK Health Insurance Agency (UKHSA) is investigating the variant to reflect this potential risk.
There is still no evidence that it causes more serious illness. And scientists are convinced that existing vaccines can protect people from this variant as well.
Although regular Delta still accounts for the majority of Covid infections in the UK, cases of "Delta Plus" or AY.4.2 have increased, rtv21.tv reports.
Recent official data suggest that 6% of cases with Covid are of this type.
There are thousands of different types or variants of Covid circulating around the world. Viruses mutate all the time, so it is not surprising to see the release of new versions.
The UK is already offering boosting doses of the Covid vaccine to people at higher risk before winter, to make sure they have the fullest protection against the coronavirus.
There is no suggestion that a new vaccine update will be needed to protect against any of the existing variants of the pandemic virus.21Media