Real-time Assessment of Community Transmission findings

23 December - REACT-1 round 16

Community infection trends in December

This study looked at swab tests from over 97,000 people across England between 23 November and 14 December. The study observed a fall of infections in November, with large drops observed in secondary school-aged children and older adults, likely due to the impact of vaccination. This was followed by a steep rise in the overall rate of infections in December, when the Omicron variant began to rapidly spread. The proportion of Omicron infections compared to Delta rapidly increased in December. 

Click here to read the peer-reviewed publication in Science. Publication title: 'Rapid increase in Omicron infections in England during December 2021: REACT-1 study'

Click here to read the pre-print report. Report title: 'Rapid increase in Omicron infections in England during December 2021: REACT-1 study'

Click here to read our news story. 'REACT study shows rapid rise in Omicron while highlighting vaccine success'

18 November - REACT-1 round 15 final

Community infection trends in October and early November

This study looked at swab tests from over 100,000 people across England between 19 October and 5 November. The findings showed that infections doubled since September but declined throughout October. A single vaccine dose in school-aged children cut the risk of infection by more than half, and the risk of symptomatic infection by two-thirds. The risk of infection was almost three times lower in people who had received a booster compared to those who had received two doses.

Click here to read the pre-print report. Report title: 'REACT-1 round 15 final report: Increased breakthrough SARS-CoV-2 infections among adults who had received two doses of vaccine, but booster doses and first doses in children are providing important protection'

Click here to access the pre-print report on medRxiv

Click here to read our news story. 'COVID-19 vaccination cuts infection risk by half in school-aged children - REACT'

4 November - REACT-1 round 15 interim

Community infection trends in late September and early October

These interim findings from the 15th round of the REACT-1 study looked at swab tests from 67,000 people across England. The study recorded the highest prevalence of infection since the programme began in May 2020, with 1.72% of people infected. The highest number of infections were in school-aged children, with 1 in 17 infected. The study also read the viral genetic code of 126 positive samples, findings all were the Delta variant, 10% of which were AY.4.2. sub-lineage which is a variant under investigation.

Click here to read the pre-print report. Report title: 'REACT-1 round 15 interim report: High and rising prevalence of SARS-CoV-2 infection in England from end of September 2021 followed by a fall in late October 2021'

Click here to read our news story: 'REACT study records highest coronavirus prevalence yet'

2 November - REACT-1 rounds 12 and 13

Coronavirus infection trends (peer-reviewed publication)

This study looked at REACT-1 data from 200,000 people across England gathered from rounds 12 and 13, carried out between 20 May and 12 July 2021. It found that despite the highly successful vaccination campaign, infections were increasing exponentially, driven by the Delta variant with high infection prevalence among younger, unvaccinated people. 

Click here to access the peer-reviewed publication in Science. Publication title: 'Exponential growth, high prevalence of SARS-CoV-2, and vaccine effectiveness associated with the Delta variant'

14 October - REACT-1 round 14

Coronavirus infection trends in September

This research from the REACT-1 programme looked at data from swab samples taken at home by around 100,000 people in England, between 9 and 27 September. The research found that 1 in 120 people had the virus during this period with R around 1. However infections were high and increasing in school-age children. The study also looked at vaccination effectiveness against infection, and how this changed over time. 

Click here to read the pre-print report. Report title: 'REACT-1 study round 14: High and increasing prevalence of SARS-CoV-2 infection among school-aged children during September 2021 and vaccine effectiveness against infection in England 

Click here to read our news story: 'Coronavirus infections flat in England but rising in school-aged children - REACT'

4 October - REACT-2

Assessing the acceptability and performance of lateral flow tests 

This research from the REACT-2 programme looked at how well people could use a type of finger-prick antibody test called a lateral flow test, and how accurate the tests were at detecting coronavirus antibodies. The research was carried out with non-healthcare key workers. 

Access the peer-reviewed publication in Open Forum Infectious Diseases here. Publication title: 'Acceptability, usability and performance of lateral flow immunoassay tests for SARS-CoV-2 antibodies: REACT-2 study of self-testing in non-healthcare key workers'

28 September - REACT-1 rounds 2-8

Symptoms linked with COVID-19 in the community (peer-reviewed publication)

This research looked at data from over a million people in England who have participated in the REACT-1 programme, identifying symptoms that are linked with having the coronavirus. Of the range of symptoms identified, seven were found to be the best predictors of having COVID-19 among symptomatic individuals. If these symptoms were included in testing criteria, the number of infections detected could therefore be increased. 

Access the peer-reviewed publication in PLOS Medicine here. Publication title: 'Predictive symptoms for COVID-19 in the community: REACT-1 study of over 1 million people'

Access the preprint report of the findings from February.

Click here to read our news story: 'COVID-19 linked with wider set of symptoms than previously thought – REACT study'

13 August - REACT-1

Duration of swab positivity

This research from the REACT-1 programme investigated how long people who are infected with the coronavirus shed virus for following a positive test. The research found that people with symptoms, and those infected with the Delta variant, tested positive for a longer period compared to those without symptoms or infected with the Alpha variant. 

• Access the preprint report here. Report title: 'Characterising the persistence of RT-PCR positivity and incidence in a community survey of SARS-CoV-2'

9 August - REACT-2

Behavioural responses following coronavirus antibody testing

This study looked at people's behaviours after they tested themselves for coronavirus antibodies as part of the REACT-2 study. The study involved a follow-up survey of almost 9,000 people which was carried out six weeks after they took their test, around half of whom were positive for antibodies and the other half negative. The study didn't find strong evidence that people changed their behaviours after testing positive, in the context of a research study. 

• Access the preprint report in Wellcome Open Research here. Report title: 'Behavioural responses to SARS-CoV-2 antibody testing in England: REACT-2 study'

4 August - REACT-1 round 13 final report

Coronavirus infection trends in June and July

The 13th round of the REACT-1 study looked at swab test data from almost 100,000 people in England between 24 June and 12 July. The research found that infections were three times lower in people who were fully vaccinated, compared to unvaccinated people. The data also suggested that people who were fully vaccinated were less likely to pass the virus on to others, due to having a lower viral load on average and therefore shedding less virus. 

• Click here to access the preprint report. Report title: 'REACT-1 round 13 final report: exponential growth, high prevalence of SARS-CoV-2 and vaccine effectiveness associated with Delta variant in England during May to July 2021'
• Click here to read our news story, 'Coronavirus infections three times lower in double vaccinated people - REACT'

22 July - REACT-2 round 4

Coronavirus antibody survey in late 2020

This study used finger-prick tests (lateral flow devices) to check for coronavirus antibodies in a random sample of 161,500 adults across England. Tests were carried out between 27 October and 10 November 2020. 5.6% of people tested positive for antibodies, a 25% rise compared to previous findings. 

• Click here to access the preprint report on medRxiv

14 July - REACT-2 round 6

Coronavirus antibody survey in May

The sixth round of the REACT-2 coronavirus antibody survey looked at data from over 207,000 people in England between 12th and 25th May 2021. The study found that almost 100% of adults had coronavirus antibodies 14 days after receiving their second COVID-19 vaccine dose. The research found high levels of vaccine uptake, although coverage was uneven with men, people living in deprived areas, those working in public-facing roles such as retail and hospitality, and people who identify as Black among those with lower vaccination rates. 

• Download the preprint report here. Title: 'Vaccine uptake and SARS-CoV-2 antibody prevalence among 207,337 adults during May 2021 in England: REACT-2 study'
• Click here to access the preprint on medRxiv‌‌
• Read our news story by clicking here. Title: 'Almost 100% of double vaccinated people in England have coronavirus antibodies'

8 July - REACT-1 round 13 interim report

Coronavirus infection trends in June and July

An interim analysis of data from the 13th round of the REACT-1 study looks at the prevalence of infection in England, based on swab tests carried out by almost 50,000 people between 24 June and 5 July. The results showed that infections continued to grow exponentially during this period, doubling every 6 days, with the R number at 1.87.

• Download the preprint report here
• Read our news story: 'Coronavirus infections continue to grow exponentially in England - REACT study'
  

24 June - REACT-2 rounds 3-5

Symptom reporting in over half a million REACT-2 participants

An analysis of questionnaire data from more than half a million people surveyed as part of our REACT-2 programme found that 1 in 20, or around 6%, had COVID-19 symptoms lasting 12 weeks or more. That means that more than two million people in England may have had long COVID, a poorly understood condition where people experience persistent symptoms after being infected with the coronavirus. Women, people who smoked, were overweight or obese, or lived in deprived areas, all had a higher risk of experiencing persistent symptoms. The risk also increased with age. 

• Download the preprint report here. Report title: 'Persistent symptoms following SARS-CoV-2 infection in a random community sample of 508,707 people'
• Read our news story: 'Over 2 million adults in England may have had long COVID - Imperial REACT'

23 June - REACT-2 study 4

Assessing finger-prick antibody tests with key workers

This study explored the use and performance of finger-prick antibody tests with key workers. The study evaluated the accuracy of the tests by comparing performance with other techniques. The study also looked at how easy they are to perform. 

• Download the preprint report: REACT-2 Study 4. Report title: 'Acceptability, usability and performance of lateral flow immunoassay tests for SARS-CoV-2 antibodies: REACT-2 study of self-testing in non-healthcare key workers'
• Access the supplementary data: REACT-2 Study 4 Supplementary Data‌
• Access the preprint report on medRxiv here. 

17 June - REACT-1 round 12

Community infection trends in late May and early June

REACT scientists tested almost 110,000 people between 20th May and 7th June. They found evidence that England's epidemic is growing exponentially, with the prevalence of infection increasing by 50% since the last testing round, from 0.1% to 0.15%. The R number was found to be 1.44. Analysis of positive swabs also found that the majority were the Delta variant first identified in India. 

• Download the pre-print report here. Report title: 'REACT-1 round 12 report: resurgence of SARS-CoV-2 infections in England associated with increased frequency of Delta variant'  (If you are unable to access the report at the link above, please download the report using this link: REACT-1 round 12 (PDF))
• Access the preprint report on medRxiv here
• Read our news story: 'Coronavirus infections rising exponentially in England - REACT study'

13 May - REACT-1 round 11

Community infection trends in April and early May

REACT scientists tested over 127,000 people in England between 15th April and 3rd May. They found that since the study's previous report in March, infections had dropped by half to 0.1% of the population, or 1 in 1000 people. The study also successfully analysed the genetic code of a small number of the positive swab samples, finding that the majority were the Kent variant while two, both in London, were the Indian variant of concern. 

• Download the pre-print report here. Report title: REACT-1 round 11 report: low prevalence of SARS-CoV-2 infection in the community prior to the third step of the English roadmap out of lockdown
• Access the preprint report on medRxiv here
• Read our news story: 'Coronavirus infections have fallen to 1 in 1000 in England - REACT study'

7 May - REACT-1 rounds 8-10

Tracing virus variants in the community from January to March 2021

REACT scientists looked at coronavirus genetic profiles from swab samples collected between January and March 2021. The majority of infections were with the Kent (B.1.1.7) variant. People infected with this variant were no more likely to report having any of the 'classic four' COVID-19 symptoms, but they were more likely to still have detectable virus antibodies 6 weeks after infection. The study also detected infections with the South African (B.1.351) variant in January, from people who had not travelled internationally, but not February or March. This suggests that this variant was spreading in the community but then faded out over time.

• Download the preprint report here. Report title 'SARS-CoV-2 lineage dynamics in England from January to March 2021 inferred from representative community samples'
• Access the preprint on medRxiv here. 

23 April - REACT-1 rounds 1-4

Community infection trends between May and September 2020 (peer-reviewed publication)

This peer-reviewed study, published in the journal Science, reports findings from more than half a million swab tests taken between May and September 2020 in England. The researchers found that infections declined between May and July 2020 but then increased gradually from mid-August, accelerating into early September 2020 at the start of the second wave. When compared to COVID-19 cases detected through routine surveillance, the study found a longer period of decline and that infections were clustered in younger age groups.

• Access the paper published in Science here. Report title: 'Resurgence of SARS-CoV-2: detection by community viral surveillance'

08 April - REACT-1 round 10

Community infection trends in March

Throughout March, and shortly after the reopening of schools, our study swabbed more than 140,000 people. The research found that the rate of new infections levelled off, or plateaued, with 1 in 500 people having the virus (0.2% of the population). This represents approximately a 60% fall since the study's previous findings in February. The study also found that infections are leading to fewer hospital admissions and deaths, which likely reflects the impact of the vaccination programme.

• Download the pre-print report here. Report title: 'REACT-1 round 10 report: Level prevalence of SARS-CoV-2 swab-positivity in England during third national lockdown in March 2021'
• Access the preprint report on medRxiv here
• Read our news story: 'Coronavirus infections levelling off in England - REACT study'

04 March - REACT-1 round 9 final

Community infection trends in February

Our study swabbed more than 163,000 people to find out how many people currently have the virus in England, and identify those who have a greater risk of infection. The study reported that 1 in 204 people are infected, or 0.49% of the population, and that the rate of decline has slowed. The study also found that ethnic minorities, health and care home workers, people working in public transport and those employed in schools, universities, childcare and education all had a higher risk of testing positive. 

• Download the pre-print report here. Report title: REACT-1 round 9 final report: Continued but slowing decline of prevalence of SARS-CoV-2 during national lockdown in England in February 2021
• Access the pre-print report on medRxiv here‌
• Read our news story: 'Fall in coronavirus infections has slowed in England – REACT study'

02 March - REACT-2

Evaluating finger-prick antibody tests

As part of the REACT-2 study, scientists evaluated the accuracy of a number of different finger-prick antibody testing kits to find out if they would be suitable for use in large-scale antibody studies.

• Read the paper in the BMJ

25 February - REACT-2 round 5

Antibody survey and attitudes towards vaccines

Our study of 155,000 people has shown that around 14% of England’s population has evidence of antibodies against the coronavirus, either from having had COVID-19 or a coronavirus vaccine. The study also looked at antibody responses in people who have had the Pfizer/BioNTech vaccine, and people's attitudes towards being vaccinated.

• Download the pre-print report here. Report title: 'REACT-2 Round 5: Increasing prevalence of SARS-CoV-2 antibodies demonstrate impact of the second wave and of vaccine roll-out in England'
• Access the pre-print report on medRxiv here‌
• Read our news article: 'Coronavirus antibodies in 14% of England’s population – Imperial REACT'

18 February - REACT-1 round 9 interim

Community infection trends in early February

The number of people infected with the coronavirus in England has dropped by over two-thirds since January. But infections are still high with around 1 in 200 people testing positive.

• Download the pre-print report here. Report title: 'REACT-1 round 9 interim report: downward trend of SARS-CoV-2 in England in February 2021 but still at high prevalence'‌‌‌
• Access the pre-print report on medRxiv here
• Read our news article: 'Coronavirus infections have fallen substantially in England – REACT study'

10 February - REACT-1 rounds 1-8

Identifying symptoms linked with COVID-19 

Our study of over a million people revealed a wide range of additional symptoms that are linked with having the coronavirus. Among these other symptoms, chills, loss of appetite, headache and muscle aches were together most strongly linked with being infected, alongside the four 'classic' symptoms.

• Download the pre-print report here. Report title: Symptom reporting in over 1 million people: community detection of COVID-19'
• Access the pre-print report on medRxiv here‌‌‌
• Read our news article: 'COVID-19 linked with wider set of symptoms than previously thought – REACT study'

28 January - REACT-1 round 8 final

Community infection trends in January 2021

A very high number of people were infected with the coronavirus in England three weeks into lockdown, with 1 in 64 people testing positive (1.57% of the population). 

• Download the pre-print report here. Report title: 'REACT-1 round 8 final report: high average prevalence with regional heterogeneity of trends in SARS-CoV-2 infection in the community in England during January 2021'
• Access the pre-print on medRxiv here
• Read our news article: 'Coronavirus infections remain high three weeks into lockdown - REACT study'

21 January - REACT-1 round 8 interim report

Community infection trends in January 2021

Coronavirus infections were not falling in the early stages of the third national lockdown in England and 1 in 63 people were testing positive with the virus.

• Download the pre-print report here. Report title: 'REACT-1 round 8 interim report: SARS-CoV-2 prevalence during the initial stages of the third national lockdown in England'
• Access the pre-print report on medRxiv here
• Read our news article: 'Coronavirus infections are not falling in England, latest REACT findings show'

27 October 2020 - REACT-2 round 2

Trends in coronavirus antibodies in England's population

Tests on more than 365,000 people in England showed that the antibody response to the virus that causes COVID-19 wanes over time.

• Download the pre-print report here. Report title: 'Declining prevalence of antibody positivity to SARS-CoV-2: a community study of 365,000 adults'
• Access the pre-print report on medRxiv here
  
• Read our news article: 'Coronavirus antibody prevalence falling in England, REACT study shows'

9 October 2020 - REACT-1 round 5 final

Community infection trends in late September and early October

An analysis of swab tests taken by 175,000 people between 18th September and 5th October found that the prevalence was rising with the virus infecting around 45,000 people each day.

• Download the pre-print report here. Report title: 'High and increasing prevalence of SARS-CoV-2 swab positivity in England during end September beginning October 2020: REACT-1 round 5 updated report'
  
• Access the pre-print report on medRxiv here
  
• Read our news article: Community coronavirus infections growing nationally, REACT study shows

1 October 2020 - REACT-1 round 5 interim

Community infection trends in late September and early October

Infections were found to have increased substantially across all age groups and areas of the country, with 1 in 200 infected. 

• Download the pre-print report here. Report title: 'High prevalence of SARS-CoV-2 swab positivity in England during September 2020: interim report of round 5 of REACT-1 study'
• Access the pre-print report on medRxiv here
  
• Read our news article:  Latest REACT findings show high number of coronavirus infections across England

11 September 2020 - REACT-1 round 4

Community infection trends in August and early September

The study showed a reversal in coronavirus trends, with infections doubling every 7 to 8 days, compared to May and June when infections were halving every 8 to 9 days

• Download the pre-print report here. Report title: 'Resurgence of SARS-CoV-2 in England: detection by community antigen surveillance'
  
• Access the pre-print report on medRxiv here
  
• Read our news article: ''Largest COVID-19 testing study shows cases are rising across England" 

13 August 2020 - REACT-2

Evaluating lateral flow tests in the lab for use in a national coronavirus antibody survey

An evaluation of a number of different finger-prick antibody testing kits found that the best performing tests are suitable for large-scale surveillance studies to monitor the progress of the pandemic. These could correctly identify individuals with coronavirus antibodies over 80% of the time, while also correctly ruling out those who don’t in more than 98% of tested individuals.

• Download the peer-reviewed publication, published in Thorax. Title: 'Laboratory Evaluation of SARS-CoV-2 Lateral Flow Assays for use in a national COVID-19 sero-prevalence survey'
• Read our news article: 'Biggest study on antibody finger-prick tests identifies promising kits'

12 August 2020 - REACT-2 round 1

Coronavirus antibody prevalence in England following the first peak of the pandemic

Findings in brief

Tests on over 100,000 people showed that slightly under 6% of the population had antibodies to the virus and had likely previously had COVID-19 by the end of June, an estimated 3.4 million people. London had the highest numbers at over twice the national average (13%), while the South West had the lowest (3%).

• Read the peer-reviewed publication in Nature Communications
• Download the supplementary figures for the report: REACT-2 Supplementary Table S1, REACT-2 Supplementary Table S2‌
• Read our news article: 'Largest study on home coronavirus antibody testing publishes first findings'

12 August 2020 - REACT-2 study 3

Usability and acceptability of antibody self-testing kits at home

This study looked at how well people could use antibody self-testing kits at home, and whether they felt these were acceptable to them. The study found high levels of usability and acceptability among adults living in England. 

• Download the peer-reviewed publication, published in Clinical Infectious Diseases. Title: 'Usability and acceptability of home-based self-testing for SARS-CoV-2 antibodies for population surveillance'
• View our infographic to find out more about the study methods and findings: REACT 2 study 3 infographic (PDF)

6 August 2020 - REACT-1 round 2

Community infection trends as England exited national lockdown

The research showed the prevalence of infection decreased to 0.077%, compared to May’s rate of 0.13% despite some lockdown restrictions being eased in June. 

• Download the pre-print report here. Report title: 'Transient dynamics of SARS-CoV-2 as England exited national lockdown'
• Access the pre-print report on medRxiv here
• Read our news article: 'Latest findings from coronavirus testing programme show decline of virus in June'

11 July 2020 - REACT-1 round 1

Community prevalence of the coronavirus in England during May 2020

Tests on more than 120,000 people carried out between 1 May and 1 June, prior to the easing of lockdown, revealed that infection rates were significantly falling, dropping by half every 8 to 9 days.

• Download the pre-print report here. Report title: 'Community prevalence of SARS-CoV-2 virus in England during May 2020: REACT study'
• Access the pre-print report on medRxiv here
• Read our news article: 'First findings published from largest home COVID-19 testing programme'