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21st June 2021
Despite the national rollout of the COVID-19 vaccine, the latest results from latest (round 12) REACT-1 study reveal that since the end of May 2021, cases of COVID-19 in England have been increasing. The results are based on random testing of approximately 110,000 people using a throat and nose swab between 20 May and 7 June 2021. Each time the results are available, the REACT-1 team compare the results with those obtained in the penultimate survey (in this case, 15 April to 3 May 2021).
For round 12, the researchers identified 135 positive samples from 108,911 valid swabs which gives a weighted prevalence of 0.15% (95% CI 0.12-0.18%). In round 11, the weighted prevalence was 0.10% (95% CI 0.08 – 0.13%) and with the latest figures, the team have estimated that the reproduction or R rate for England is 1.44, an increase from 1.07 in the previous round.
As with earlier rounds, the REACT-1 team have observed considerable regional variability. For instance, the weighted prevalence is highest in the North West (0.26%) and lowest in the South West (0.05%). The prevalence is also very different across age ranges. Among those aged 5-12 years and 18-24, there is a much higher prevalence (0.35% and 0.36% respectively) compared to those aged 65 years and over (0.07%). It is also still higher among those of Asian ethnicity (0.28%) compared with people of white ethnicity (0.13%) and varies considerably with the household size. For instance, the prevalence ranges from 0.07% among those living alone to 0.34% where there are six or more household members.
In line with other data, the results from round 12 show that around 90% of swab samples subjected to genomic analysis were for the Delta variant. As this latest variant is known to be more transmissible, the REACT-1 authors have estimated a doubling time of infections of 11 days.
25th January 2021
The Real-time Assessment of Community Transmission (REACT-1) is a longitudinal study of the community prevalence of COVID-19, led by a team from Imperial College, London. The study regularly reports on the prevalence of COVID-19 collected from a random sample of more than 120,000 people in England, identified from national health service records linked to a patient’s GP. Invited participants, who vary in age from 5 years to over 65, are sent a nasopharyngeal swab kit for home testing and which is then collected and analysed for COVID-19. The study has been collecting data since June 2020 and provides an important snapshot of the prevalence of COVID-19 in the community.
The REACT-1 (8a) covers the period 6-15 January 2021. Researchers found a total of 1962 positive swabs from 142,909 individuals giving a weighted prevalence of 1.58% (95% CI 1.49-1.68%). Interestingly, they note that this represents the highest prevalence since the study began in May 2020, when the prevalence was 0.16%. Moreover, it is more than 50% higher than round 7 (the previous data collection period), between November to December 2020). However, using a growth model, the team could not find any evidence of either a growth or decay in prevalence and estimated the transmission rate, R to be 1.04. In analysing mobility data from the Facebook app, the team found a decreased activity at the end of December 2020 that began to rise again in January 2021. As a result, they speculated that this increased activity might have caused the rise in cases. Across the country, the prevalence more than doubled in the London area from last round 7 (1.21%-2.47%) and in the East of England (0.59%-1.74%). However, infection rates decreased in Yorkshire and The Humber and remained broadly similar to round 7 in the East Midlands. The age-related prevalence showed an increase among those aged 18 to 24 (0.99%-2.51%) and among those aged 65 years and over (0.41%-0.94%). In discussing their findings, the authors noted that there was no continued decline in prevalence during the third national lockdown but rather a slight initial decline followed by a plateau or possible increase. They also cautioned that if rates do not fall there will be an increase in hospitalisations, which will negatively impact on healthcare delivery.
REACT-1 round 8 interim report; SARS-CoV-2 prevalence during the initial stages of the third national lockdown in England.