REACT-1: real-time assessment of community transmission of coronavirus (COVID-19) in September 2020

Updated 29 October 2020

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Methodology

A representative cross-section of volunteers tested themselves with swabs between 18 and 26 September 2020. Swabs were analysed using polymerase chain reaction (PCR).

Results

Over the 9 days for which data are available to date, overall weighted prevalence of infection in the community was 0.55% (0.47%, 0.64%) Out of 84,610 swab results, 363 were positive. This was significantly higher than the prevalence of 0.125% (0.096%, 0.154%) measured during August 2020 and the highest observed prevalence of any round since this study started reporting in May.

The reproduction number R for the period between 20 August and 26 September was estimated to be 1.47 (1.40, 1.53) which is slightly lower than that measured during August 2020 at 1.7 (1.4, 2.0). When using only round 5 data from 18 to 26 September, the reproduction number R is estimated to be 1.1 (0.7, 1.5).

The highest rates of infection were at 0.96% (0.68%, 1.36%) in young adults aged 18 to 24 years, up from 0.25% (0.15%, 0.41%) in August. However, the prevalence of infection increased across all age groups between August and September 2020. Infection rates in people ages 65 years and over increased 7-fold with a prevalence rate of 0.29% (0.23%, 0.37%) from 18 September to 26 September, compared with a prevalence rate of 0.04% (0.03, 0.07%) between 20 August and 7 September.

The prevalence of infection increased in all regions between August 2020 and September 2020. The highest unweighted prevalence of infection was in the North West at 0.86% (0.69%, 1.06%) followed by 0.78% (0.54%, 01.13%) in the North East and 0.54% (0.39%, 0.76%) in Yorkshire and the Humber.

Asian and Black ethnicity was associated with higher prevalence of infection at 0.82% (0.55%, 1.20%) and 0.93% (0.45%, 1.91%) respectively. People of Black and Asian ethnicity had a 2-fold higher rate of infection compared with White participants. Prevalence has increased across all ethnic groups since August 2020.

The prevalence was highest amongst those who reported classic COVID-19 symptoms (high temperature, new continuous cough, loss of smell or taste) at 2.15% (1.75%, 2.63%). This was significantly higher than for those reporting other symptoms at 0.51% (0.40%, 0.65%) or no symptoms at 0.31% (0.26%, 036%).

Conclusion

During the period 18 September to 26 September 2020, SARS-CoV-2 virus was circulating with significantly higher prevalence than between 20 August to 7 September and infections had increased substantially across the generations and country, with 1 in 200 infected.

Subsequent rounds of REACT-1 will allow further accurate assessment of trends in prevalence and transmission.