Covid-19 infections are doubling in England every nine days and the growth in transmission is no longer fastest in the North, according to interim results from round 6 of the REACT-1 study.

The national prevalence of infection in the community was 1.28 per cent, according to analysis of a representative sample of 85,000 volunteers who tested themselves between October 16-25.

This was significantly higher than a prevalence of 0.60 per cent measured in September to early October, and the highest observed prevalence of any round of the study since it started reporting in May.

Data collected between October 16-25 suggest the national reproduction number, R, is 1.56 in comparison with the estimate for round 5 in September, of 1.16.

There has been an increase in infections in all age groups between rounds 5 and 6, with the highest relative increase in the 55-64 year-old age group.

Infection rates in people aged 65 years and over more than doubled to 0.75 per cent from October 16-25, compared with 0.33 per cent from September 18 to October 5.

The highest rate of infection was still seen in 18-24 year olds at 1.71 per cent, up from 1.21 per cent. A substantial increase was positive tests was seen in both primary and secondary aged children.

The prevalence of infection has increased in all regions since September and early October 2020. Unweighted prevalence of infection was highest in the North West at 1.91 per cent, Yorkshire and The Humber at 1.83 per cent and in the North East at 1.35 per cent.

REACT-1 is a large population surveillance study being undertaken in England that examines the prevalence of the virus causing Covid-19 in the general population. The study was commissioned by the Department of Health and Social Care (DHSC) and is carried out by Imperial College London, Imperial College Healthcare NHS Trust and Ipsos MORI.