Covid infections are falling in Britain, the Office of National Statistics (ONS) has confirmed after registering a drop in prevalence for the first time since daily cases started to fall.

Daily cases in the UK have halved since the peak around July 15, but some scientists believed it was an artificial effect caused by schools breaking up, the good weather or a drop in testing.

Now the ONS figures show that the falls were real, with the number of people infected in England dropping from one in 65 to one in 75 in the week ending July 31. 

In Wales, around one in 230 people are estimated to have had Covid in the week to July 31 – down from one in 160 in the previous week. In Scotland, the ONS estimates that around one in 120 people had Covid, down from one in 110 in the previous week, although Northern Ireland has seen increases. 

Experts welcomed the general fall in infection levels as "good news", while the ONS said it was "encouraging".

Sarah Crofts, the head of analytical outputs for the Covid Infection Survey, said: "After rising for some weeks as a result of the delta variant, it is encouraging that infections have now fallen across England, Wales and Scotland. They are still increasing in Northern Ireland, where delta emerged slightly later."

Map of UK's seven-day Covid-19 infection rate, by local authority

The ONS figures are thought to be more reliable than daily reported cases because they come from a representative sample of the population and include asymptomatic infections which may never show up in the national figures. 

However, because people can still be infectious for some time after testing positive, the ONS figures are several weeks behind the national data – meaning it has been impossible to check whether the recent falls were real until now.

Commenting on the ONS figures, Paul Hunter, professor in medicine at the University of East Anglia, said: "The latest report from ONS provides further confirmation that infection rates really are falling in the UK. In Northern Ireland, however, cases are still rising.

"The fall has been most notable in younger age groups. The percentage fall was not as great as we saw in case numbers but this was largely due to the fact that the ONS study reports on PCR positives and people who become positive can remain so for more than two weeks, so there will always be a lag in decline identified by ONS and by clinical sampling.

"Whether this decline will continue or reach an equilibrium before schools return in September is not yet clear. We may see numbers remaining around the level they are at now."

On Friday, a further 31,808 cases were reported – a slight rise from the same time last week – but the seven-day average is still six per cent lower than the previous week.

Hospital admissions have also started to fall, with 788 patients testing positive for Covid at the most recent day for which data is available, August 2.

Experts said the ONS figures were likely to continue falling for the next few weeks, matching what has already seen in the reported data.

"Given that confirmed cases on the dashboard are still generally falling in England, Wales and Scotland, I’d expect the falling trends in the CID prevalence figures to continue there for a little longer at least," said Kevin McConway, emeritus professor of applied statistics at The Open University.

"What I take from this is that the falling trends in new confirmed cases on the dashboard, first in Scotland and later in England and Wales, aren’t just happening because of changes in who is turning up to be tested, and do reflect what’s actually going on in terms of infections."