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.

Publications
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). https://doi.org/10.1038/s41467-021-21237-w

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) https://doi.org/10.1101/2021.07.21.21260926

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) https://doi.org/10.1101/2021.02.26.21252512

Round 6: Vaccine uptake and SARS-CoV-2 antibody prevalence among 207,337 adults during May 2021 in England: REACT-2 study. (Preprint) https://doi.org/10.1101/2021.07.14.21260497

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.

Publications
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) https://doi.org/10.1101/2021.07.14.21260488

Christina J Atchison, Maya Moshe, Jonathan C Brown, Matthew Whitaker, Nathan C K Wong, Anil A Bharath, Rachel A McKendry, Ara Darzi, Deborah Ashby, Christl A Donnelly, Steven Riley, Paul Elliott, Wendy S Barclay, Graham S Cooke, Helen Ward, Validity of Self-testing at Home With Rapid Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Antibody Detection by Lateral Flow Immunoassay, Clinical Infectious Diseases, 2022 https://doi.org/10.1093/cid/ciac629

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.

Publications
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.

Publications
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.

Machine learning to support visual auditing of home-based lateral flow immunoassay self-test results for SARS-CoV-2 antibodies

As part of the REACT-2 programme, during the COVID-19 pandemic, antibody test kits, for use at home, were used to estimate how many people had COVID antibodies. These estimations indicated how many people had been exposed to the virus or had antibodies due to vaccination. However, some positive test results can be very faint, and be mistaken as negative. In our work, 500,000 people reported their antibody test results and submitted a photograph of their test. We designed a computerised system—a highly specialised artificial-intelligence (AI) system—that had high agreement with experts and could highlight potential mistakes by the public in reading the results of their home tests. This AI system makes it possible to improve the accuracy of monitoring COVID antibodies at the population level (e.g. whole country), which could inform decisions on public health, such as when booster vaccines should be administered.

Publications

Access the full report here: REACT ALFA Pipeline Full Technical Report.

Nathan C. K. Wong, Sepehr Meshkinfamfard, Valérian Turbé, Matthew Whitaker, Maya Moshe, Alessia Bardanzellu, Tianhong Dai, Eduardo Pignatelli, Wendy Barclay, Ara Darzi, Paul Elliott, Helen Ward, Reiko J. Tanaka, Graham S. Cooke, Rachel A. McKendry, Christina J. Atchison & Anil A. Bharath Machine learning to support visual auditing of home-based lateral flow immunoassay self-test results for SARS-CoV-2 antibodies Commun Med 2, 78 (2022).
https://doi.org/10.1038/s43856-022-00146-z

Information for study participants

If you gave permission for Imperial College London to link your health data held by NHS Digital and other NHS bodies to your survey data, we will bring data from March 2015 into the REACT cohort. We will continue to link your data into the future. You have the right to withdraw your consent to our processing of your personal data, please see the privacy policy for details.