Worrying new data shows one in 20 secondary school pupils in England are believed to have had Covid last week.
Figures from the Office for National Statistics (ONS) reveal that around 4.6 per cent of children in England in school years 7 to 11 – around one in 20 – are likely to have tested positive.
This is the highest positivity rate for any age group.
Around one in 85 people in private households in England are likely to have had Covid-19 in the week to September 25, up from one in 90 in the previous week, according to the Office for National Statistics (ONS).
One in 85 is the equivalent of about 658,800 people.
At the peak of the second wave in early January, around one in 50 people in England were estimated to have coronavirus.
But while the number of people testing positive for the virus is estimated to have increased in England and Wales, it has fallen slightly in Scotland and Northern Ireland.
The rate of children testing positive is estimated to have increased among those aged from two to school year 11, and there were also early signs of a possible increase for those aged 70 and over, the ONS said.
The percentage testing positive decreased for those from school year 12 to age 24 and levelled off for people aged 35 to 69, while the trend was uncertain for those aged 25 to 34.
The figures for secondary school children were described as “extraordinarily high” by Kevin McConway, emeritus professor of applied statistics at the Open University.
“The rate in that age group didn’t start increasing really fast until roughly mid-September, so a little time after schools had reopened,” Professor Conway said.
“It’s true that children of these ages are very unlikely to get seriously ill if they are infected. But they can pass on the infection to others.
“It’s pleasing, however, to see a continuing fall in the rate of testing positive in those aged between school year 12 and age 24 – who, of course, have now been vaccinated in large numbers.
“The ONS estimate for that group is that one in 90 would test positive, and that rate has been falling pretty steadily at least from mid-August, when it was about one in 30.”
All children aged 12 and over in the UK are now able to have a first dose of Covid-19 vaccine, which means those in school years 8 to 11 in England, as well as some in year 7, can get the jab.
The ONS estimates are based on a regular sample of nose and throat swabs taken in the community.
They do not include people in care homes, hospitals or other institutional settings.
In Wales, around one in 55 people are estimated to have had Covid-19 in the week to September 25, up from one in 60 the previous week and the highest level since the week to December 23 2020.
The estimate for Northern Ireland has dropped from one in 60 to one in 65.
The figure had reached one in 40 for the week to August 20, which was the highest since estimates began for Northern Ireland in September 2020.
For Scotland, the ONS estimates around one in 55 people had Covid-19 in the week to September 25, down from one in 45 the previous week, which had been the highest level since estimates began for Scotland in October 2020.
Among the regions of England, the percentage of people testing positive for Covid-19 is estimated to have increased in the East Midlands, north-west England, south-west England and Yorkshire and the Humber.
It has fallen in London and north-east England, while the trend for all other regions is uncertain.
Yorkshire and the Humber had the highest proportion of people of any region likely to test positive for coronavirus in the week to September 25, at around one in 55.
London had the lowest estimate at around one in 130.