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 has estimated that the reproduction or R rate for England is 1.44, an increase from 1.07 in the previous round.
National variation
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 five to 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.
