Four people have died in the UK from the Covid-19 variant first identified in India in the first known domestic deaths from the strain.
The four deaths took place between May 5 and May 12, government data shows, however the fatalities do not necessarily mean the variant is more lethal.
The figures come as ministers consider allowing tens of millions in the UK to have their second vaccines early in a rush to contain the spread of the variant.
Vaccines Minister Nadhim Zahawi said on Friday the government “ruled nothing out in terms of whatever action we take regionally or nationally”, including allowing younger people to receive the shot early.
Scientists said an increase in hospital admissions from the variant would put the fourth and final step of England's lockdown easing on June 21 in doubt.
Public Health England has so far recorded 1,313 cases of the variant – more than double the 520 cases reported up to May 5.
The strain is rising fastest in northern England, particularly in Bolton and Tyneside, but also in parts of London, in the south of the country.
Prime Minister Boris Johnson insisted on Thursday that the third step of indoor mixing would go ahead as planned on Monday despite admitting he felt anxious about the threat posed by the strain.
Mr Zahawi reminded Muslims celebrating Eid Al Fitr to do so cautiously, to “break the cycle of transmission”. Many of the areas affected by the Indian variant have a large Muslim population.
"It's the second day of Eid today and I know many families will want to celebrate the end of Ramadan but just be careful – follow the rules, do it outdoors and be careful when you socially interact," he said on Sky News.
Mr Zahawi said indoor mixing would proceed from next week but those most at risk from the new variant could receive their second vaccine dose early to prevent them from being admitted to hospital.
“The clinicians will look at all of this to see how we can flex the vaccination programme to make it as effective as possible to deal with the surge in this variant,” he said.
"They will make those decisions and we will be ready to implement them – whether it's vaccinating younger cohorts, multigenerational households and, of course, the older groups."
At least one local council attempted to distribute doses faster on Thursday. Everyone over the age of 18 in Blackburn was encouraged to receive their injection, until the government intervened and the council clarified that only over-18s with health conditions would be vaccinated.
Analysis suggests the UK’s vaccine drive prevented 11,700 deaths up to the end of April.
A PHE study also found at least 33,000 hospital admissions were avoided in those aged 65 and older.
Prof Nick Loman, a genomics adviser to PHE, said the vaccine appeared to be effective against the Indian variant and he supported distributing doses faster in areas where there was a surge in case numbers.
"I'm feeling quite good about the vaccines," he told the Today programme on BBC Radio 4.
“We do have options, such as changing the dosing schedule and changing the way we approach vaccinations. I think there is a role for using vaccines to target particularly affected areas.”
He said it was still unclear whether the Indian strain was more infectious than previous variants, but the situation should be monitored.
“If the virus has increased transmissibility we should start to see it in each part of the country take over from other viruses that are circulating, and that means the UK variant,” he said.
“That’s not obvious at this stage.”
Lockdown easing 'in doubt'
Prof Paul Hunter from the University of East Anglia said if a further increase in the Indian variant "puts pressure on the NHS then step four [of lockdown easing] is in doubt".
"If the epidemic continues to increase with the Indian variant at the same rate that it has over recent weeks we’re going to have a huge number of cases by June," he said.
"The big question is how many people getting the new Indian variant will end up requiring hospitalisation and at the moment the hospitalisation rate doesn’t seem to be increasing yet."
Officials are hoping that surge testing of a large number of asymptomatic people in affected areas will be able to keep the Indian variant in check. The tactic helped to contain the South African variant.
But the Department of Health said ministers "cannot rule out reimposing economic and social restrictions at a local or regional level if evidence suggests they are necessary to contain or suppress a variant which escapes the vaccine".
Meanwhile, Welsh First Minister Mark Drakeford said he was taking a “cautionary approach” and decided to leave some restrictions in place for the next step of lockdown easing that takes place on Monday.
“We were considering a small number of further easements on Monday but have decided to hold back," he said. The lifting of restrictions will now depend on advice from the Sage committee of scientific advisers.
"We continue to take a cautionary approach in case the Indian variant is on the march," he said.
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