The Covid-19 variant that originated in India is now believed to be dominant in the UK, with early evidence suggesting it may lead to an increased risk of being admitted to hospital compared with the Kent variant.

A total of 12,431 cases of the Indian variant, also known as the Delta variant, have been confirmed in the UK up to June 2, according to Public Health England (PHE).

This up 79% from the previous week’s total of 6,959.

PHE’s June 3 risk assessment for the Indian variant found that vaccines were less effective against the strain compared to the Kent mutation.

The findings, which have been determined with a “high degree of confidence” according to PHE, also suggest people are more at risk of hospital admission if infected with the variant.

However, figures show that more than two-thirds of people found with the Indian strain were unvaccinated.

Some 278 people with the Indian variant attended A&E in the most recent week, resulting in 94 people being admitted to hospital overnight.

This compares with 201 A&E attendances in the previous week, with 43 admissions.

The majority of admissions continue to be people who have not been vaccinated, PHE said.

Of the 479 people who attended A&E in England between February 1 and May 31 and who were confirmed as having the Indian variant, 309 were unvaccinated while 18 had received both doses.

And of the 137 cases where attendance at A&E resulted in an overnight inpatient admission, 90 were unvaccinated while seven had received both doses.

Of the 12,431 Indian variant cases so far confirmed in the UK, 10,797 are in England, 1,511 in Scotland, 97 in Wales and 26 in Northern Ireland.

Bolton in Greater Manchester continues to be the most affected local area, where cases have risen by 795 to 2,149.

Blackburn with Darwen in Lancashire has seen 368 new cases, bringing it to 724 in total.

In Bedford there have now been 608 confirmed cases, with 349 in Leicester, 278 in Manchester and 223 in Birmingham.

PHE figures show that from February 1 to May 31, there were 9,427 cases of the Indian variant recorded in England, of which 5,172 were in unvaccinated people.

Of the 137 cases that resulted in a hospital inpatient admission, just seven of those were people who had received both vaccine doses, 24 involved patients who received their first dose more than 21 days ago, and 90 were patients who had not received any dose.

Some 17 people died over the same period with the Indian variant, of which two had received both vaccine doses and 11 were unvaccinated.

Meanwhile, there were 140 outbreaks of the Indian variant in schools and 62 in workplaces between January 4 and June 1.

Early evidence suggests there may be an increased risk of being admitted to hospital for this variant compared with the Kent, or Alpha, variant – but “more data is needed to have more confidence in that finding”, PHE added.

Dr Jenny Harries, chief executive of the UK Health Security Agency, said: “With this variant now dominant across the UK, it remains vital that we all continue to exercise as much caution as possible.

“The way to tackle variants is to tackle the transmission of Covid-19 as a whole. Work from home where you can, and practice ‘hands, face, space, fresh air’ at all times.

“If you are eligible and have not already done so, please come forward to be vaccinated and make sure you get your second jab. It will save lives.”

The latest PHE data also suggests there have been 97 confirmed Covid-19 outbreaks in primary and secondary schools that have had at least one variant case linked to them over the most recent four-week period.

This is the equivalent of around one in 250 schools.

Outbreaks and clusters of Covid-19 in primary and secondary schools are at low levels, but there has been a slight increase over recent weeks in line with higher levels of the Indian variant circulating in the community.

There are “encouraging signs” that the transmission rate in Bolton has begun to fall and that “actions taken by residents and local authority teams have been successful in reducing spread”, PHE said.

Meanwhile the Government said a further 5,274 lab-confirmed cases of coronavirus had been recorded in the UK as of 9am on Thursday, the highest single-day figure since March 26.