REACT study records highest coronavirus prevalence yet


Woman on tube wearing a face mask

New data from the Imperial-led REACT coronavirus monitoring programme reveal the highest number of infections since the study began in May 2020.

Interim results from swab tests taken at home by over 67,000 people between 19th and 29th October show that 1 in 58 tested positive during this period, or 1.72% of people. For school-aged children the figure was around 1 in 17.

This is more than double the number of people who tested positive in the study’s previous testing round in September when 1 in 120, or 0.83%, had the virus in England.

The prevalence rose across ages and in almost all regions from September to October 2021, with infections estimated to have been highest on 19/20 October, consistent with Pillar 2 testing data. However, the latest data show a recent fall with a reproduction number (R) below 1. This is similar to the pattern of infections observed this time last year when infections dropped at half term, after which they rapidly grew again. However at the time, the prevalence of infection was lower than current rates, at 1.30%.

These interim findings from the ongoing REal-time Assessment of Community Transmission (REACT-1) programme, carried out in partnership with Ipsos MORI and commissioned by the UK Health Security Agency, are available here in a pre-print report and will be submitted for peer-review. The full report, containing data through early November, will be available soon. Data are continually reported to the government to inform decision-making.

High prevalence in school-aged children

For this latest round of the REACT study, 67,208 people swabbed themselves at home and their samples were analysed by PCR testing. 1,021 of these were positive, giving an overall weighted prevalence of 1.72%. Weighting is where the researchers make adjustments to their calculations to ensure the sample reflects England’s population.

"Children could be driving up infection rates by spreading the virus to others in their homes." Prof Paul Elliott School of Public Health, Imperial

The highest prevalence was found in children aged 5-12 years at 5.85% (1 in 17), followed by secondary school-aged children aged 13-17 at 5.75%. 18-24-year-olds had the lowest prevalence at 0.59%, followed by those aged 75+ at 0.67%. In the latter age group, and for those aged 65-74, infections had approximately doubled from the previous round.

Prevalence was also more than four times higher in households with one or more children at 3.09%, compared to those without children (0.75%).
Professor Paul Elliott, director of the programme from Imperial’s School of Public Health, said: “These very recent data show that infections are still very high, especially in school-aged children. We continue to find that households with children have a higher prevalence of infection, indicating that children could be driving up infection rates by spreading the virus to others in their homes.

“The vaccination programme in children ages 12 and above should help control infection rates in children of secondary school age, helping to ensure their education does not suffer due to the impact of the pandemic.”

Regional differences

Test results from this latest round showed that the South West had the highest infection prevalence at 2.18%, which is four times higher than the previous round. Since the last round infections rose across all areas except Yorkshire and The Humber. Looking at the most recent data only, there has been a fall in prevalence in East Midlands, East of England and the South West.

"These findings are a powerful reminder that the pandemic is far from over." Dr Jenny Harries Chief Executive of the UK Health Security Agency

The study also read the viral genetic code of 126 positive samples from this round, finding that all were the Delta variant. 10.3% of these were the AY.4.2. sub-lineage, defined as a variant under investigation, meaning it is being monitored.

Dr Jenny Harries, Chief Executive of the UK Health Security Agency, said: “Although the number of hospitalisations and deaths remain lower than in previous peaks, these findings are a powerful reminder that the pandemic is far from over and remains a serious threat to health and wellbeing. This new data strongly reinforces the need for all eligible age groups to get vaccinated and to take mitigating measures such as wearing a face covering in crowded places and ensuring good ventilation indoors.

“This is particularly urgent for older people whose immunity may be waning given that several months have passed since they received their jabs. I strongly encourage everyone who is eligible for a third dose or a booster shot to come forward without delay.

Monitoring the COVID-19 epidemic

The REACT-1 study is tracking current coronavirus infections in the community by testing more than 100,000 randomly selected people each month over roughly a two-week period. The study recruits new people each month to help ensure the sample represents the wider population and offers a high-resolution snapshot of the situation across a particular time period.

"Today’s report sends an important message that we need to stay vigilant as we head into the winter months." Sajid Javid Health and Social Care Secretary

This is different from the ONS COVID-19 Infection Survey which runs continuously and samples the same people over time to understand household transmission. Because the studies use different methods, this means that sometimes they report different figures.

Health and Social Care Secretary Sajid Javid said: “Today’s report sends an important message that we need to stay vigilant as we head into the winter months.

“Vaccines continue to be our first line of defence against this disease and it is crucial we all get jabbed to keep the virus at bay. Whether you have yet to receive your first dose, second dose or if you are eligible for your booster jab – the best thing you can do is get vaccinated to protect yourself and those around you.”

Kelly Beaver, Managing Director, Public Affairs at Ipsos MORI said: “This interim report shows the highest levels of prevalence that the REACT Study has found at any point during the pandemic. This reinforces the need for continued vigilance and for people to take up the vaccine as well as the booster when offered to them. Thank you to all those who have voluntarily participated in the REACT research programme; they are playing an important part in supporting management of the pandemic.”


Justine Alford

Justine Alford
Institute of Global Health Innovation

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