Independent report

REACT-1 study of coronavirus transmission: April 2021 final results

Updated 13 May 2021

Methodology

A representative cross-section of volunteers tested themselves with swabs from 15 April to 3 May inclusive. Swabs were analysed using polymerase chain reaction (PCR).

Results

Over the 19 days of the completed round of testing, referred to as round 11 (15 April to 3 May), out of 127,408 swab results, 115 were positive giving a weighted prevalence overall of 0.11% (0.08%, 0.13%), or 11 people per 10,000 infected, down by ~45% from round 10 (11 March to 30 March) where weighted prevalence was 0.20% (0.17%, 0.23%).

There was evidence of a decline over the period of round 10 (11 March to 30 March) to round 11 (15 April to 3 May), with an estimated R of 0.91 (0.87, 0.94). Within round 11 (15 April to 3 May), an R of 0.97 (0.71, 1.27) has been estimated with 42% probability that R >1.

Regional R between rounds 10 to 11 was below 1 with probability ≥99% in northern regions and East Midlands. There was a 94% probability R>1 in South East. Weighted prevalence was similar across regions ranging from 0.07% (0.03%, 0.17%) in the South West to 0.13% (0.07, 0.27%) in West Midlands and 0.13% (0.07%, 0.24%) in London.

Weighted prevalence has fallen in 55 to 64 year olds from 0.17% (0.12%, 0.25%) in round 10 (11 March to 30 March) to 0.06% (0.04%, 0.11%) in round 11 (15 April to 3 May). Weighted prevalence was higher in 25 to 34 year olds at 0.21% (0.12, 0.38%) than in the 55 to 64 year olds.

For round 11, lineages have so far been determined for 26 of the 116 positive swab tests obtained. We identified B.1.1.7 and B.1.617.2:

  • 92.3% (75.9%, 97.9%, n=24) were B.1.1.7
  • 7.7% (2.1%, 24.1%, n=2) were B.1.617.2

Both samples from the B.1.617.2 lineage were detected in London in people who did not report returning from abroad in the previous 2 weeks.

Conclusion

During the period 15 April to 3 May (round 11), SARS-CoV-2 virus was circulating with a lower prevalence than round 10 between 11 March to 30 March, with 11 in 10,000 infected.

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