REACT-1 study of coronavirus transmission: March 2021 final results
Updated 23 April 2021
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Methodology
A representative cross-section of volunteers tested themselves with swabs from 11 March to 30 March inclusive. Swabs were analysed using polymerase chain reaction (PCR).
Results
Over the 20 days of the completed round of testing, referred to as round 10, out of 140,844 swab results, 227 were positive giving a weighted prevalence overall of 0.20% (0.17%, 0.23%), or 20 people per 10,000 infected, down by ~60% from round 9 (4 February to 23 February) where weighted prevalence was 0.49% (0.44%, 0.55%).
There was evidence of a decline over the period of round 9 (4 February to 23 February) to round 10 (11 March to 30 March), and a halving time of 26 (23, 31) days has been estimated, corresponding to R of 0.84 (0.82, 0.86). Within round 10 (11 March to 30 March), an R of 1.00 (0.81, 1.21) has been estimated with 51% probability that R >1.
These results suggest a slow down in the rate of decline, with prevalence plateauing during round 10. At regional level, R over the period of rounds 9 (4 February to 23 February) to 10 (11 March to 30 March ranged from 0.75 (0.68, 0.81) in South East to 0.95 (0.87, 1.03) in Yorkshire and The Humber.
There were substantial falls in weighted regional prevalence: in South East from 0.36% (0.29%, 0.44%) in round 9 to 0.07% (0.04%, 0.12%) in round 10; London from 0.60% (0.48%, 0.76%) to 0.16% (0.10%, 0.26%); East of England from 0.47% (0.36%, 0.60%) to 0.15% (0.10%, 0.24%); East Midlands from 0.59% (0.45%, 0.77%) to 0.19% (0.13%, 0.28%); and North West from 0.69% (0.54%, 0.88%) to 0.31% (0.21%, 0.45%).
At sub-regional scale, areas of higher prevalence remain in round 10 (11 March to 30 March) in parts of North West, and Yorkshire and The Humber.
The highest weighted prevalence of swab-positivity was found in those aged 5 to 12 years at 0.41% (0.27%, 0.62%) compared with the lowest in those aged 65 to 74 and 75 and over at 0.09%.
Conclusion
During the period 11 March to 30 March (round 10), SARS-CoV-2 virus was circulating with a lower prevalence than round 9, between 4 February to 23 February with 20 in 10,000 infected.
Subsequent rounds of REACT-1 will allow further accurate assessment of trends in prevalence and transmission.