LONDON (Reuters) -The Delta variant of concern first identified in India is now dominant in Britain and might have an increased risk of hospitalization compared to the Alpha variant, Public Health England said on Thursday.

There were 5,472 new cases of the Delta variant reported in latest weekly figures, taking the total confirmed cases of the variant to 12,431, PHE said, adding it had overtaken Alpha, the variant first identified in England’s Kent, as Britain’s dominant variant.

The Delta variant is also thought to be more transmissible than Alpha, and Prime Minister Boris Johnson has warned that it could derail plans for lockdown restrictions in England to end on June 21.

“With this variant now dominant across the UK, it remains vital that we continue to exercise caution particularly while we learn more about transmission and health impacts,” said Jenny Harries, Chief Executive, UK Health Security Agency.

PHE said that early evidence suggested there may be an increased risk of hospitalization for Delta, also known as B.1.617.2, compared to Alpha, known as B.1.1.7, but more data was needed in order to have more confidence in that finding.

PHE said there continued to be a “substantially increased growth rate for Delta compared to Alpha” but did not update on the transmissibility advantage of the variant.

Officials have previously said that Delta could be from a few percentage points to 50% more transmissible than the Alpha variant, and the extent of that advantage could determine whether restrictions can be lifted on June 21.

(Reporting by Alistair Smout and William James; Editing by Kate Holton)