Health officials are investigating a new coronavirus variant which has caused 49 cases of infection, mostly concentrated in Yorkshire and the Humber region.
Public Health England (PHE) has been monitoring the VUI-21MAY-01 variant since April.
It has been designated Variant Under Investigation - which is currently less serious than a Variant of Concern.
The variant is from a lineage which was designated a signal in monitoring on May 6, based on an unusual mutation profile, Public Health England said.
PHE said there was "currently no evidence that this variant causes more severe disease or renders the vaccines currently deployed any less effective".
It added: "PHE is carrying out increased laboratory testing to better understand the impact of the mutations on the behaviour of the virus.
"All appropriate public health interventions are being undertaken, including additional contact tracing and targeted testing. Where cases have been identified, additional follow-up of cases, testing of contacts and targeted case finding will limit the spread of variants."
PHE said it would provide more information on the variant later today in its Variant Technical Briefing.
