Woman working in laboratory

The Real-time Assessment of Community Transmission (REACT) programme is one of the largest, most significant pieces of research looking at how the COVID-19 pandemic is progressing in England. 

The study is being carried out by a world-class team of scientists, clinicians and researchers at Imperial College London, in partnership with Ipsos MORI, and was commissioned by the Department of Health and Social Care. Explore our study's findings below. 

Our findings - 2022

June - REACT-1

Vaccine effectiveness against infection (peer-reviewed publication)

Our study looked at how well booster (third) doses, and vaccination of 12-17-year-olds, reduced the risk of coronavirus infection, using data from REACT-1 collected between June and November 2021.

We found that in children aged 12-17, vaccines cut the risk of infection by around two-thirds, while adults who received a third vaccine dose were less likely to test positive compared to those who received two doses.

Read the peer-reviewed publication in eClinicalMedicine. Publication title: 'Breakthrough SARS-CoV-2 infections in double and triple vaccinated adults and single dose vaccine effectiveness among children in Autumn 2021 in England: REACT-1 study'

 

24 May - REACT-1 round 19

Community infection trends in March (peer-reviewed publication)

This study looked at swab testing data from over 109,000 people between 8 and 31 March 2022. The research recorded the highest coronavirus prevalence since the study began in May 2020 and documented the BA.2 Omicron variant replacing the BA.1 strain.

Visit the Science website to access the publication. Paper title: 'Twin peaks: the Omicron SARS-CoV-2 BA.1 and BA.2 epidemics in England'

23 May - REACT-1

Symptoms of coronavirus variants

This study looked at the most common symptoms that people had when infected with different coronavirus variants. The research included over 1.5 million people in England, who took part in REACT-1 between May 2020 and March 2022. The study showed changing symptom profiles associated with the different variants over that period. Omicron BA.2 was associated with reporting more symptoms, with greater disruption to daily activities, than BA.1.

Visit the medRxiv website to access the preprint. Paper title: 'Variant-specific symptoms of COVID-19 among 1,542,510 people in England'

12 April - REACT-2 rounds 3-5, 6

Symptom reporting in over 600,000 REACT-2 participants (peer-reviewed publication)

This study analysed questionnaire data from more than 600,000 people surveyed as part of our REACT-2 programme between September 2020 - February 2021 (study rounds 3-5) and May 2021 (round 6). The research found that 1 in 20, or around 6%, had COVID-19 symptoms lasting 12 weeks or more in rounds 3-5, which fell to 21.6% in round 6. Women, people who smoked or vaped, those with obesity, and people living in deprived areas all had a higher risk of experiencing persistent symptoms. The risk also increased with age.

Access the peer-reviewed publication in Nature Communications. Publication title: 'Persistent COVID-19 symptoms in a community study of 606,434 people in England'

6 April - REACT-1 round 19 (final round)

Community infection trends in March

The final testing round of the REACT-1 coronavirus surveillance study found that around 1 in 16 people had the virus as of 31 March, or 6.37% of people. This is more than double the study's previous findings and 40% higher than the first Omicron peak in January. Infections were found to be likely slowing or decreasing in younger people, while they were rising in older age groups.

Click here to read the preprint report. Report title: 'Twin peaks: the Omicron SARS-CoV-2 BA.1 and BA.2 epidemics in England'

Click here to read our news story: '1 in 16 infected with the coronavirus as REACT study records highest rates yet'

4 April - REACT-1

The Omicron wave

This study used PCR and sequencing data from REACT-1 to study the dynamics of the Omicron wave in England. The researchers estimate an initial peak in national Omicron prevalence of 6.89% during January 2022, followed by a resurgence in infections in England during February-March 2022 as the more transmissible Omicron sub-lineage, BA.2 replaced BA.1 and BA.1.1.

Access the preprint publication on medRxiv. Report title: 'The new normal? Dynamics and scale of the SARS-CoV-2 variant Omicron epidemic in England'

10 March - REACT-1 round 18

Community infection trends in February

This study looked at almost 95,000 swab tests taken between 8 February and 1 March, showing that around 1 in 35 was infected during this period. This is the second highest the study has recorded since it began testing in May 2020. Infections were flat or possibly rising in those aged 55+, while there was also a substantial increase in the proportion of the BA.2 Omicron 'stealth' variant.

Click here to read the preprint report. Report title: The Omicron SARS-CoV-2 epidemic in England during February 2022

Click here to access the preprint report on medRxiv.

Click here to read our news story: 'Coronavirus infections remain high while Omicron ‘stealth variant’ rises - REACT'

16 February - REACT-2

Population antibody responses following COVID-19 vaccination (peer-reviewed publication)

Our researchers carried out the largest study to date looking at factors linked with antibody responses to COVID-19 vaccination. The study identified a declining antibody response with increasing age, a lower response in men compared with women, and higher responses in those receiving an mRNA vaccine (e.g. Pfizer/BioNTech) compared to a viral vector vaccine (i.e. AstraZeneca). There were also lower responses in those with obesity and other co-occurring conditions, such as diabetes.

Click here to read the publication in Nature Communications. Report title: 'Population antibody responses following COVID-19 vaccination in 212,102 individuals'

25 January - REACT-1 round 17

Community infection trends in January


This study looked at over 100,000 swab tests taken in January, finding that coronavirus infections were declining in early January and then plateaued at a high level, with 1 in 23 infected during this period. Infections were highest in 5-11-year-olds, and lowest in those aged 75 and above. However, infections rose 12-fold in the oldest age group since December.

Click here to read the report. Report title: 'Post-peak dynamics of a national Omicron SARS-CoV-2 epidemic during January 2022'

Click here to read the preprint report on medRxiv

Click here to read our news story: 'Fall in coronavirus infections in England may have stalled at high level - REACT'

24 January - REACT-1

Vaccine effectiveness in England

This peer-reviewed paper, published in The Lancet Respiratory Medicine, looked at swab testing data from over 100,000 people gathered for the REACT-1 study. The scientists then estimated community-based prevalence of the coronavirus and vaccine effectiveness against infection.

Click here to read the publication. Report title: 'SARS-CoV-2 infection and vaccine effectiveness in England (REACT-1): a series of cross-sectional random community surveys'

Our findings from 2021

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'

Our findings

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'

Our findings

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. 

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. 

Our findings

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. 

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. 

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. 

Our findings

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.

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. 

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. 

Our findings

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. 

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. 

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.

Our findings

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.

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.

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. 

Our findings

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.

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.

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.

2021 findings

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.

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). 

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.

Our findings from 2020

15 December 2020 - REACT-1 round 7 final

Community infection trends during England's second national lockdown

The rate of new coronavirus infections in England was found to no longer be on a downward trend and had flattened in mid-December.

30 November 2020 - REACT-1 round 7 interim report

Community infection trends during England's second national lockdown

Coronavirus infections were found to be declining in England at the end of November, with R below 1. 1 in 100 people were found to test positive.

Our findings

12 November 2020 - REACT-1 round 6 final

Community infection trends in early November

Coronavirus infections were continuing to rise in early November but the findings suggested early signs that the rate was slowing down.

29 October 2020 - REACT-1 round 6 interim report

Community infection trends in early November

The infection prevalence was found to have doubled since the previous round of testing, with 96,000 new infections each day.

Our findings

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.

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.

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. 

Our findings

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

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.

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%).

Our 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. 

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. 

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.