A slowdown in the growth in new Covid-19 cases across the UK has raised hopes that the third wave may be shorter and shallower than previously feared, as vaccines continue to blunt the force of the Delta variant first identified in India.

A further 10,476 people tested positive for Covid-19 in the UK on Friday, a rise of 29 per cent on a week ago, as 11 deaths were reported, down from 17 the week before.

More than four-fifths of UK adults have now received a first dose of the vaccine, after the rollout was extended to those aged 18 to 25. In London, four football stadiums, including Chelsea FC’s Stamford Bridge, are opening their doors this weekend as part of a drive to vaccinate 100,000 people a day in the capital, where uptake is lagging behind the rest of the country.

The average number of new cases reported each day across the UK has risen fourfold from 2,020 on June 5 to more than 8,740 on June 18, but the rate of increase has slowed markedly in recent days.

Week-on-week growth in new cases has halved from 67 per cent on June 9 to 33 per cent on June 18, suggesting that the early period of spread may have given way to a more steady climb.

It remains too early to say whether the slowdown will continue, as it may be, at least in part, a result of the half-term break in schools during the first week of June.

Chart showing that there are signs that the growth rate in new infections in the UK may be slowing, though this could be a temporary lull caused by half-term

But data show that the vaccine programme continues to limit the impact of the Delta variant. Of the 806 people hospitalised with the variant to date, 88 per cent were unvaccinated or had received only one dose of the vaccine, according to Public Health England. Leon Danon, data analytics professor at Bristol university and a member of the UK scientific pandemic influenza group on modelling (SPI-M), said he was “cautiously positive”, but stressed he would like to see the damping of the growth rate “repeat itself over several weeks” before drawing firm conclusions.

“In some areas, infections are still doubling every week, which is worrying,” said Danon. “Patchiness has been a characteristic of this pandemic and looks like it will be of the third wave too.”

The reproduction rate, or R value, was unchanged from last week at between 1.2 and 1.4, according to official government data, meaning it is estimated every 10 people infected with the virus will infect between 12 and 14 others.

Meanwhile, the rate of new infections slowed, according to the Office for National Statistics’ infection survey, which estimates the total of both asymptomatic and symptomatic cases. The number of people testing positive rose by 7 per cent to 118,800 in the week to June 12, compared with a rise of 13 per cent the week before.

Prof Tim Spector, an epidemiologist from King’s College London whose Zoe study has been tracking Covid symptoms in participants, said the third wave looked like it would be “very small wave or a large ripple”, adding that he expected new cases to peak in around a fortnight.

Spector cited data from Wales as an “encouraging sign” for the rest of the UK. In Wales, first-dose vaccination coverage is nearing 90 per cent, around 8 percentage points above the UK average. As a result, infection rates fell to one in 1,500 people in the week to June 12, the lowest across the UK, according to the ONS.

“[With] the combination of this wave being limited to the young and meeting this wall of immunity, it should be running out of people to infect soon. I expect it to be short and shallow . . . way less dramatic than winter or spring,” Spector said.

He added that the government should offer vaccine booster doses “sooner rather than later” to avoid “waning immunity” after the summer.

But hospital admissions from Covid-19 continue to rise. There were 1,373 patients admitted in the week to June 14, a 40 per cent increase on the week before.

However, Chris Hopson, chief executive of NHS Providers, which represents healthcare leaders, said that while some hospitals have had to “dial back a little” on elective recovery, medics were confident they would be able to “continue making good headway” through the NHS backlog throughout the third wave.