Health officials are investigating a new Covid variant which has caused 49 cases of infection, mostly in Yorkshire and the Humber region, BBC reports.
Public Health England (PHE) has been monitoring the VUI-21MAY-01 or AV.1 variant since April.
PHE said there was "currently no evidence that this variant causes more severe disease or renders the vaccines currently deployed any less effective".
The agency said additional testing and tracing was being carried out.
Dr Kev Smith, from PHE, said scientists had been watching and sequencing the variant since the "strange combination of mutations" were spotted a few weeks ago.