Coronavirus infections among children increased in England last month after schools reopened, a study has found.

The surge kept overall cases high even as COVID-19‘s prevalence among adults fell, the research showed.

The epidemic was estimated to be growing among those under 17, with an R number estimated at 1.18, according to the REACT-1 study led by Imperial College London.

An R number above 1 means the coronavirus outbreak is growing exponentially – but below 1 means the case rate is shrinking.

By contrast, the figure for 18 to 54-year-olds was estimated at 0.81, indicating that the epidemic is contracting – while for those over 55 it was broadly steady.

The percentage of 13 to 17-year-olds with COVID-19 was 2.55% between 9 September to 27 September, and 2.32% among children aged 5 to 12.

This compares with below 1% for every adult age group.

The difference in case rates can be partially attributed to the higher vaccination figures among adults.

Over 90% of adults have had at least one dose of a COVID-19 jab, whereas the figures are lower among children.

Vaccines were only made broadly available for 12 to 15 year olds last month.

Researchers said vaccinating more school-aged children and unvaccinated adults will help reduce the potential for transmission.

The study of 100,527 swabs found that 0.83% of people had COVID-19 from 9 September to 27 September, compared with 0.63% in the earlier part of July.

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Education unions recently called for the reintroduction of extra safety measures in schools after official estimates showed around 270,000 secondary pupils had COVID-19 in the week to 2 October.

The NASUWT union said schools need more support with on-site testing and called on the government to consider reinstating the requirement for pupils who are contacts of a positive case to self-isolate.

The education secretary and health secretary have written to parents of secondary school and college students this week, urging them to ensure their children are getting tested regularly and also encouraging them to get vaccinated against coronavirus.