But the UK Health Security Agency said the sharp increase in cases across England is not being followed by a similar increase in hospitalisation and death.
Public Health England figures show 851 cases of the Delta variant – first identified in India – had been recorded in Doncaster by July 7.
That was 191 more than the 660 cases recorded the week before.
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Those identified in the latest week were among 20,867 cases of the variant recorded across Yorkshire – the third-worst affected of England's nine regions.
The North West continued to have the highest numbers identified, with 60,669 Delta variant cases recorded there.
Across the UK, 54,268 more cases were recorded in the last week to reach a total of 216,249 – a 34 per cent increase.
PHE said the Delta variant currently accounts for around 99 per cent of cases that are sequenced in the UK.
Dr Jenny Harries, chief executive of the UKHSA, said: "The data continues to show that the sharp increase in cases that we are seeing is not being followed by a similar increase in hospitalisation and death.
"This is because two doses of the available vaccines offer a high level of protection against the Delta variant.
"Getting both jabs is the best way to ensure you and the people you love remain safe, so we once again urge everyone to come forward as soon as they are eligible."
Different PHE figures show that up to June 21, the majority of people admitted to hospital with the Delta variant in England were unvaccinated – around three-quarters of those under 50, and a third of those aged 50 and above.
As of June 21, there had been 257 deaths in England of people who were confirmed as having this strain of coronavirus and who died within 28 days of a positive test.
Of the 216,249 cases recorded across the UK, 180,643 have been identified in England, 28,559 in Scotland, 3,666 in Wales and 3,381 in Northern Ireland.