The coronavirus vaccine developed by Pfizer-BioNTech is likely to be just as effective against a highly transmissible mutant strain of the virus that was discovered in the U.K., according to a study by the two companies.

The variant, known as B.1.1.7., was estimated to have first emerged in the U.K. in September. It has an unusually high number of mutations and is associated with more efficient and rapid transmission.

The characteristics of the variant had led to concerns about the effectiveness of Covid vaccines against it. However, research published on preprint server bioRxiv showed “no biologically significant difference in neutralization activity” between the laboratory tests on B.1.1.7 and the original strain of the coronavirus.