About one in 60 people in England had Covid-19 last week, according to estimates published on Friday.
The prevalence of infection was up for a third straight week, having been at about one in 70 the previous week, according to the Office for National Statistics (ONS).
At the peak of the second wave in early January, about one in 50 people were estimated to have coronavirus. The latest estimate of one in 60 equates to about 890,000 people.
While the government has continued to insist it will rely on vaccines rather than lockdowns to navigate a difficult winter, some experts have expressed concern about the rise.
Prevalence was highest once again in secondary school pupils, prompting Prof Christina Pagel, the director of UCL’s clinical operational research unit, to reiterate criticism of preparations for the return of children to schools. An estimated 8.1% of all secondary pupils were infected, up from 6.93% the previous week.
“When are we going to say enough is enough and protect kids?” tweeted Pagel, who co-authored a piece in the Guardian last week that noted countries such as France and Germany were using extra measures as part of a “vaccine-plus strategy” designed to keep cases and deaths low.
Cases have also increased among people in England over 50, who were among the first to receive vaccines and are now being given booster shots.
In Wales, about one in 45 people are estimated to have had Covid-19 in the week to 9 October, up from one in 55 the previous week and the highest since estimates began in July last year.
The latest estimate in Northern Ireland is one in 120, up from 130 the previous week but well below the recent peak of one in 40 for the week to 20 August.
For Scotland, the ONS estimates about one in 80 people had Covid-19 in the week to 9 October, down from one in 60 the previous week.
Catherine Noakes, a professor of environmental engineering for buildings at the University of Leeds and an expert on indoor air quality and airborne infection, said measures were needed to stop the situation getting worse in the coming months.
“We have higher cases than the rest of Europe. We have less controls than the rest of Europe,” she said, emphasising the need for ventilation, mask wearing and a continued focus on hand washing.
The percentage of people testing positive for Covid is estimated to have increased in all regions of England except the East Midlands, London and the north-east, the ONS said.
In the north-west, south-west and Yorkshire and the Humber, about one in 50 people were likely to test positive last week.