The level of coronavirus circulating among secondary school pupils has risen severely with one in 15 now infected, according to the latest figures.
This is up from one in 20 the past week and equivalent to around 270,000 children testing positive for Covid in the week to 2 October.
But while the number of people testing positive overall for the virus is estimated to have increased in England, it has fallen in Scotland and Northern Ireland.
Around one in 70 people in private households in England had Covid-19 in the week to 2 October, up from one in 85 the past week, according to the Office for National Statistics (ONS).
One in 70 is the equivalent of about 786,300 people. At the peak of the second wave in early January, around one in 50 were estimated to have coronavirus.
The ONS said rates have increased for those in school years seven to 11, people aged 35 to 49 and those aged 70 and over.
Around one in 15 children in school years seven to 11 are estimated to have had Covid-19 in the week to 2 October – the highest positivity rate for any age group.
Kevin McConway, emeritus professor of applied statistics at the Open University, said that with around 4 million children in that age group in England, one in 15 equates to around 270,000 testing positive.
He said that based on separate ONS estimates on long Covid prevalence, this could average about 13,500 could go on to have long Covid symptoms, and almost 7,000 will have symptoms that limit their day-to-day activity.
Prof McConway additional: “That’s rather a lot of children who will have their schooling and other activities disrupted.
“I think the main necessary action here is to get on with vaccinating those aged 12-15 as quickly as possible – though, given that it takes time for the vaccine to become effective, that’s nevertheless not going to bring down the infection rate in this group all that fast.
“I’m certainly not suggesting school closures or anything like that, but I don’t think it’s an option to do nothing.”
Unison’s assistant general secretary Jon Richards said masks and school bubbles needed to be reintroduced and the vaccine rollout to 12 to 15-year-olds sped up.
He additional: “The government can no longer look the other way while coronavirus rates rocket in secondary school-age children and are nevertheless unacceptably high in dominant.
“Pupils have faced more than a year and a half of disruption to their education and ministers must pull out all the stops to keep children in classrooms.
“These figures underline how the government’s current approach is woefully inadequate.”
The ONS figures also showed that positivity rates for the over-70s are nevertheless low at one in 170, but this is up from one in 190 the past week.
Sara Crofts, head of analytical outputs for the ONS Covid-19 infection survey, said: “There is a mixed picture of infection trends across the UK once again, with the largest increase seen in England.
“This has been largely pushed by a notable increase among secondary school pupils, likely reflecting their return to school in September.”
The percentage of people testing positive for Covid-19 is estimated to have increased in all regions except the east of England where the trend is uncertain, the ONS said.
Yorkshire and the Humber and the East Midlands had the highest proportion of people of any vicinity likely to test positive for coronavirus in the week to 2 October, at around one in 55. London and eastern England had the lowest at around one in 90.
In Wales, around one in 55 people were estimated to have had Covid-19 in the week to 2 October, unchanged from the past week and nevertheless the highest since the week to 23 December 2020.
In Northern Ireland, the latest calculate is one in 130, down from one in 65 the past week, and for Scotland it was around one in 60, down from one in 55 the past week.
Additional reporting by agencies
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