The Indian coronavirus variant is now dominant in a fifth of areas in England, Sky News analysis has found.
The latest data shows the B.1.617.2 variant – now referred to as Delta – was dominant in 67 of 315 local authorities (21%) where at least five cases were found for the two weeks ending 22 May.
This means that in those areas, the variant accounted for between 51% and 100% of cases.
In total, 230 local authorities (73%) had reported at least one case of the variant, according to the most recent data from the Wellcome Sanger Institute.
Meanwhile, cases are still growing in London and the South East.
The Indian variant made up 66.7% of new cases in England in the week ending 22 May, according to the most recent Wellcome Sanger data.
But an analysis of the latest figures by Tom Wenseleers, professor of biostatistics at the University of Leuven in Belgium, suggests it could be as high as 76%.
The Kent variant – B.1.1.7 – that emerged in the South East in December accounted for almost all reported cases in England until early April.
When the Indian variant was first identified that month it started to grow quickly in areas such as Bolton, Blackburn with Darwen, and Bedford.
But it has now spread to most areas, with infections nationwide doubling around every eight days, according to Alex Selby, a mathematician at the University of Cambridge.
With the Kent variant now only dominant across 39 local authorities (12%), the Indian one is now spreading the fastest nationwide.
It is also far more transmissible than the older one, by up to 70%, according to Mr Selby.
Bolton still has the highest levels of variant cases in the country.
But the latest data released by Public Health England, for the week ending 19 May, shows that variant infections there and in other so-called ‘hotspots’ are starting to plateau.
In the town, infections started to increase among teenagers and then spread to younger adults, but as yet there hasn’t been a similar increase in cases in older, double-vaccinated age groups.
The hope is the vaccine is working and has given a significant proportion of the more vulnerable, older people protection against the variant.
Research has shown that two vaccine doses reduces the risk of severe illness from the variant by up to 88%.
So if we are entering a third wave of cases, it is unlikely to result in more hospital admissions and deaths.
“There’s not been much of an increase in hospital admissions so far,” said Paul Hunter, professor in medicine at the University of East Anglia, which he says is encouraging.
“When cases increased like they did last time, hospital admissions increased by more and sooner. So that gives me hope,” he added.
This could be why vaccines minister Nadhim Zahawi has said he wants all over-50s fully vaccinated by 21 June.
But as independent SAGE member Professor Christina Pagel points out, even with the vaccine rollout, not everyone is protected.
“If cases get really high, even with vaccines, it will still be a problem,” she said.
“The variant will find those people who are not vaccinated and that small number for whom the vaccine doesn’t work.”
With this additional risk of the variant evading vaccines, the government’s aim to ease COVID restrictions fully on 21 June could be put in jeopardy.
Prime Minister Boris Johnson said the data is “still ambiguous” on how well jabs are protecting the vulnerable and the NHS, but a final decision will be made on 14 June.