The REACT-2 programme measures the prevalence of antibodies to SARS-CoV-2 in a random sample of the adult population in England. From June 2020 to May 2021, over 900,000 people took part, helping us to understand how many people had been infected with the virus and to identify the groups most at risk. It has also measured the waning of antibodies over time, and the impact of the vaccination programme on antibody prevalence in the population. The findings provided the Government with data on the unequal burden of COVID-19, the likely impact of previous infection and vaccination, informing public health policy.

Round1: Ward, H., Atchison, C., Whitaker, M. et al. SARS-CoV-2 antibody prevalence in England following the first peak of the pandemic. Nat Commun 12, 905 (2021).

Rounds 1-3: Ward H, Cooke GS, Atchison C, et al. Prevalence of antibody positivity to SARS-CoV-2 following the first peak of infection in England: Serial cross-sectional studies of 365,000 adults. Lancet Reg Health Eur. 2021;4:100098. doi:10.1016/j.lanepe.2021.100098

Round 4: Increasing SARS-CoV-2 antibody prevalence in England at the start of the second wave: REACT-2 Round 4 cross-sectional study in 160,000 adults. (Preprint)

Round 5: REACT-2 Round 5: increasing prevalence of SARS-CoV-2 antibodies demonstrate impact of the second wave and of vaccine roll-out in England. (Preprint)

Round 6: Vaccine uptake and SARS-CoV-2 antibody prevalence among 207,337 adults during May 2021 in England: REACT-2 study. (Preprint)

REACT-2: A Nationwide Coronavirus Antibody Study - Imperial College London and Ipsos MORI

REACT-2: A Nationwide Coronavirus Antibody Study

Imperial College London and Ipsos MORI worked together to establish REACT-2, a nationwide at home antibody study with the aim to assess how far COVID-19 infection has already spread. Antibodies are essential in our fight against disease and are a part of the immune system which is able to build an innate response to antigens caused by disease. To test for antibodies a finger prick test is used. As part of REACT-2, nearly 1 million participants were sent test kits.

REACT-2 included a number of sub-studies to evaluate self-antibody testing and ensure that large numbers of people would be able to take part:

Clinical and laboratory evaluation of antibody tests

This laboratory study evaluated the performance of finger-prick antibody tests in NHS staff who previously had COVID-19 and in 500 pre-pandemic samples from key workers, and selected the best test to use in the main study.

Flower B, Brown JC, Simmons B, et al Clinical and laboratory evaluation of SARS-CoV-2 lateral flow assays for use in a national COVID-19 seroprevalence survey Thorax 2020;75:1082-1088.

Moshe M, Daunt A, Flower B, et al. SARS-CoV-2 lateral flow assays for possible use in national covid-19 seroprevalence surveys (React 2): diagnostic accuracy study BMJ 2021; 372 :n423 doi:10.1136/bmj.n423

SARS-CoV-2 Antibody Lateral Flow Assay for antibody prevalence studies following vaccine roll out: a Diagnostic Accuracy Study (Preprint)

Acceptability and usability of antibody tests

This tested the acceptability and usability of home-based antibody testing with 300 public volunteers. They were invited to identify any issues and concerns with carrying out finger-prick antibody tests at home, and worked with us to improve the design of the kits and instructions for the larger studies.

An expanded study then further explored the usability of home-based antibody testing. Tests were sent to 14,000 randomly selected members of the public to explore whether they can perform the finger-prick test at home and read the results correctly as well as identify any issues in delivering to a large group of people.

A further study looked at whether home antibody testing led to people changing their behaviour.

Atchison C, Pristerà P, Cooper E, et al. Usability and Acceptability of Home-based Self-testing for Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Antibodies for Population Surveillance. Clin Infect Dis. 2021;72(9):e384-e393. doi:10.1093/cid/ciaa1178

Redd R, Cooper E, Atchison C et al. Behavioural responses to SARS-CoV-2 antibody testing in England: REACT-2 study. Wellcome Open Res 2021, 6:203

Key worker study

This study compared the accuracy and acceptability of tests in non-healthcare key workers (employed by the police and fire service), and measured the prevalence of infection.

Davies B, Araghi M, Moshe M, et al. Acceptability, Usability, and Performance of Lateral Flow Immunoassay Tests for Severe Acute Respiratory Syndrome Coronavirus 2 Antibodies: REACT-2 Study of Self-Testing in Nonhealthcare Key Workers. Open Forum Infect Dis. 2021;8(11):ofab496.