Covid-19 infections in children in England rose in September after schools returned from summer holidays, helping to keep cases high even as there was a fall among adults, a large prevalence study showed.

The REACT-1 study, led by Imperial College London, is the latest to find that more children are getting infected with Covid-19 following the reopening of schools at the start of September.

The study found that the epidemic was growing among those under 17, with an estimated reproduction “R” number of 1.18. An R number above 1 implies exponential growth, while a number below 1 implies the epidemic is shrinking.

The epidemic was estimated to be shrinking in 18-54 year-olds, with an R number of 0.81, while the epidemic was broadly steady among those over 55.