LONDON — A newly-discovered mutation of the delta variant is being investigated in the U.K. amid worries that it could make the virus even more transmissible and undermine Covid-19 vaccines further.

Still, there are many unknowns surrounding this descendent or subtype of the delta variant — formally known as AY.4.2 — which some are dubbing the new “delta plus” variant.

U.K. government health officials have said it’s too early to tell whether the mutation poses a greater risk to public health than the delta variant, which itself is significantly more infectious than the original Covid-19 strain (and its successor, the alpha variant).

But they have stated that they are monitoring the mutation very closely: it now accounts for 6% of U.K. Covid cases that have been genetically sequenced at a time when infections in the country are rising rapidly.