The UK has ruled out reducing the gap between doses of Covid-19 vaccines in a bid to speed up getting two jabs into more people, even as the latest data showed infections soaring again.

NHS leaders and scientists have raised concerns about Boris Johnson’s plan to lift all the remaining restrictions on July 19 when millions will not be fully immunised as the latest data showed cases jumped by 74 per cent week-on-week.

The UK prime minister is expected next week to give the green light to lifting remaining curbs as he seeks to return England to normality after almost 18 months in which the pandemic has constrained daily life. A series of announcements, on everything from mask-wearing to foreign travel, is expected in the coming days.

Speaking at Chequers on Friday where he was holding talks with German chancellor Angela Merkel, Johnson said the vaccines had played “a pretty decisive role” in breaking the link between infections, death and serious disease. “We are confident we will be able to proceed . . . on July 19,” he added.

Several people familiar with the UK vaccination programme said it remained on track to meet its target of ensuring two-thirds of adults have had the protection of two jabs, while all over 18s will have been offered a single dose, before the final lockdown easing.

But hopes that the UK might be able to speed up the vaccination programme by closing the gaps between doses of BioNTech/Pfizer (the jab being used most widely on the under-40s) from eight to just three weeks were dashed by the government’s main advisory body. The shorter period was tested in clinical trials and used in the early weeks of the BioNTech/Pfizer rollout in December.

The Joint Committee on Vaccination and Immunisation this week confirmed it was “recommending an interval of 8 to 12 weeks between doses of all the available Covid-19 vaccines”. It said this gap would “avoid confusion and simplify booking, and will help to ensure a good balance between achieving rapid and long-lasting protection.”

Chart showing that UK Covid cases are rising as steeply now as in the last wave, but hospital metrics are climbing more slowly

Some public health leaders have recently reported difficulty in accessing supplies of BioNTech/Pfizer. Ruth Rankine, of the NHS Confederation, who represents networks of GPs who have run the bulk of the vaccination programme, suggested supplies may have been a factor in the decision not to reduce the gap between the two jabs.

But government insiders close to the vaccination programme denied supply constraints were behind the decision not to close the gap between doses. “We have two Pfizer batches now coming in per week, we have plenty to cover all cohorts,” one said. “It’s all about inventory management and uptake.”

Some vaccination centres had decided, on their own initiative, to shorten the dosing interval but had been “slapped on the wrist” and told to stop, according to one person close to the programme.

“Even if there was all the supply in the world, NHS England would still be telling people to wait those eight weeks because we want the vaccines to make the maximal impact,” one public health director in the north west of England said,

Prof Anthony Harnden, deputy chair of the JCVI said that regardless of supply constraints the minimum eight-week gap was preferable as it meant young people, who may not receive boosters in the autumn, had “robust and long-lasting protection”.

More than 85 per cent of the UK’s adult population had received a first dose of a Covid vaccine while 63 per cent were fully vaccinated, according to the latest data released on Friday.

The sharp jump in the case number has fuelled concerns among scientists and health leaders that removing almost all the remaining restrictions in little over two weeks’ time comes with significant risk.

“We may have weakened the link between infections, hospitalisations and deaths but this significant increase in infections with the Delta variant raises serious concerns,” said Professor Lawrence Young, a virologist at Warwick Medical School. One risk was that, as the virus spread it would “continue to generate new variants increasing the risk that one will pop up that is more vaccine resistant,” he added.

Rankine said that ministers seemed to have focused their attention on hospitals, where admissions have risen at a much slower rate than cases, boosting hopes that the vaccine programme has helped sharply reduce the link with severe illness.

But this ignored the impact the current surge was having on primary care and community services, Rankine added. “The headlines are focusing on low hospitalisation rates but what that masks, of course, is the pressure being felt outside of hospitals in supporting patients with Covid symptoms.”

Chart showing that around three per cent of cases currently result in hospital admission, much lower than the ratio during previous waves

Hospital leaders, too, remain concerned about the impact of continued high levels of community infections. Latest figures showed admissions rising by 16.5 per cent over the past seven days, still far below the 74 per cent rise in infections over the same period.

One senior hospital administrator said that the backlog of postponed treatments built over past 18 months have left his NHS Trusts dealing with demand “at 120 per cent of normal levels . . . So the practical impact of relatively small increases in Covid hospitalisations is bigger than it looks from the numbers.”

Meanwhile, business leaders are pushing in the other direction and broadly backed the full reopening, although there are concerns that a rushed return to offices could lead to a rise in cases among employees.

They have urged ministers to clarify what the rules will be after July 19. “We need more than a week’s notice on whether [working from home] guidance will remain, how offices should operate after July 19, and what the social distancing implications will be,” said John Foster, director of policy at the CBI.

Foster also said companies needed to know if there would be a change in self-isolation rules at the same time, as they felt current guidance was needlessly forcing their staff to stay at home.

“One employee gets sick and then before you know it you’ve got a decent chunk of the workforce having to self isolate, even if they then test negative. That’s exactly the kind of thing the government needs to look at if we’re to learn to live with the virus,” he added.

Additional reporting by George Parker