REACT-1: real-time assessment of community transmission of coronavirus (COVID-19) in January 2021
Updated 23 April 2021
Applies to England
© Crown copyright 2021
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Methodology
A representative cross-section of volunteers tested themselves with swabs from 6 January to 15 January, inclusive (a small number of tests included were obtained from 30 December and after 6 January). Swabs were analysed using polymerase chain reaction (PCR).
Results
Swab results reported for the period 25 November to 3 December are referred to as round 7b. Swab results reported for the period 6 January to 15 January are referred to as round 8a.
Over the 10 days of the completed round of testing, out of 142,909 swab results, 1,962 were positive, giving a weighted prevalence of 1.58% (95% CI, 1.49%, 1.68%) or 158 people per 10,000 infected. This is the highest prevalence recorded by REACT-1 since it started in May 2020 and represents a greater than 50% increase from 0.91% in round 7b (25 November to 3 December). Within round 8a, the estimated R was at 1.04 (95% CI, 0.94, 1.15). Based on data from a limited number of days, prevalence may have started to rise at the end of round 8a (6 January to 15 January).
Despite a substantial gap between rounds 7b and 8a, changes in prevalence according to region, age and other characteristics may indicate key drivers of the epidemic.
Between rounds 7b (25 November to 3 December) and 8a (6 January to 15 January), there were changes in national prevalence at regional level. Regional prevalence was highest in London where weighted prevalence more than doubled from 1.21% to 2.80%. Prevalence also increased in South East from 0.75% to 1.68%, South West from 0.53% to 0.94%, East of England from 0.59% to 1.74%, and West Midlands from 0.71% to 1.76%. There was an apparent decrease in prevalence in Yorkshire and The Humber, and prevalence was broadly similar (comparing rounds 7b and 8a) in East Midlands and North East.
Patterns of national weighted prevalence by age group showed that between round 7b (25 November to 3 December) and round 8a (6 January to 15 January), prevalence increased in all adult age groups. Prevalence in round 8a was highest in 18 to 24 year olds with a weighted prevalence of 2.51%. Prevalence in those aged 65 and over more than doubled from 0.41% in round 7b to 0.94% in round 8a.
Despite some uncertainty, age-prevalence patterns varied substantially by region. There were large increases from round 7b to round 8a at older ages in London, South East, and East of England..In round 8a (6 January to 15 January) London had the highest weighted prevalence nationally at greater than 2% in those aged 55 to 64 and in those 65 years and over. Patterns in Yorkshire and The Humber, North East and East Midlands did not show increases between rounds 7b and 8a in older adult ages. Prevalence was over 4% in London in those aged 18 to 24 years in round 8a.
Large household size, living in a deprived neighbourhood, and Black and Asian ethnicity were all associated with increased prevalence. There was an increase in prevalence from the smallest to the largest households rising from 1.20% in single person households to 3.46% in households of seven or more people. People living in neighbourhoods in the two most deprived quintiles had prevalence of 1.88% and 1.92% compared with 1.26% for those in the least deprived. Participants of Black and Asian ethnicity had increased prevalence at 3.42% and 2.61% respectively compared with 1.45% among white participants.
Both healthcare and care home workers, and other key workers, had increased odds of swab-positivity compared to other workers in round 8 at 1.66 (1.38, 2.00) and 1.35 (1.20, 1.53) respectively.
Conclusion
During the period 6 January to 15 January, SARS-CoV-2 virus was circulating with a higher prevalence than between 25 November to 3 December with 158 in 10,000 infected. There was no strong evidence for either growth or decay in prevalence averaged across the period 6 January to 15 January.
Subsequent rounds of REACT-1 will allow further accurate assessment of trends in prevalence and transmission.