There have not been any recent rises in Covid-19 infections among younger high school pupils, an expert has said.

Sarah Croft, senior statistician for the Office for National Statistics (ONS) Covid-19 Infection Survey, told Times Radio that there has not been any recent leaps in cases among children in school years 7 to 11.

But the main increase in infections appears to be among those in school year 12 up to those in their mid-20s.

The latest data shows that 0.14% of children aged two to school year 6 are estimated to be infected, a rate which has remained largely unchanged in recent weeks.

Among secondary school children in years 7 to 11, it is estimated that 0.35% of this age group would currently test positive for Covid-19.

The figure has remained at around 0.3% – ranging from 0.28% to 0.35% – since May 23.

Among older teenagers – including those in the final school years 12 and 13 – and young adults to the age of 24, the ONS estimated that around 0.79% would test positive for Covid-19, a rate that has been rising in recent weeks.

Ms Croft told Times Radio: “What we’re seeing at the moment is the main sort of increase seems to be in school year 12 to age 24 – so older teenagers and those in their early 20s.

“In terms of other age groups, we’re seeing school years 7 to 11, but that has stayed at about 0.3% for several weeks now, we haven’t seen any recent increases there.”

Meanwhile scientists studying the symptoms of Covid-19 are due to publish their latest update on Wednesday.

The main symptoms currently reported by people taking part in the ONS Covid-19 Infection Survey are fatigue, headache, fever and a cough.

A separate study – the Zoe Covid Symptom study – recently reported that a headache, sore throat and runny nose are now the most commonly reported symptoms.

And the main classic symptoms of Covid-19, according to the NHS, are a high temperature, a new, continuous cough and/or a loss or change to a person’s sense of smell or taste.

Asked about symptoms, Ms Croft added: “We are due to publish the latest data tomorrow.

“But the last data we published on symptoms tended to report fatigue, headache, fever and a cough as the main symptoms of Covid-19 but the very latest data will be published tomorrow.”

She said that in England in May one in 1,100 people were infected but now it is around one in every 440 people.

For the latest data, in the week to June 19, around three quarters of cases were the Delta variant, which was first identified in India.