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Some papers detailing the results from the REACT-2 home antibody testing programme have been published. Some are currently in preprint form*, and others have been published** in The BMJ Thorax and Clinical Infectious Disesases.
Dr Alexander Edwards, Associate Professor in Biomedical Technology, Reading School of Pharmacy, University of Reading, said:
“This is a great illustration of how useful rapid antibody tests can be for us to understand spread across populations. Without knowing how many people have been infected, in different locations, we cannot make informed decisions about how we tackle an outbreak. Whilst swab testing for virus remains the best way to identify people currently infected, this cannot be used to study past infection. This is why ‘serosurveillance’, that at first sight may not seem as useful as diagnosing an individual patient, is one of our most critical tools for public health systems to tackle outbreaks. The extent of infection confirmed in this study seems to be similar to other studies using antibody testing, which in itself is useful to know – we really don’t want any new surprises as we begin to gain a fuller understanding of this particular virus. This data is also vital to make our epidemiology models more accurate, so that we can use them to make informed decisions.
“This is an appropriate use of rapid tests used by volunteers at home, because the aim of the study is not to make a diagnosis or guide the behaviour of an individual. The test result won’t be used to tell someone they are ‘safe’ to undertake specific work or visit vulnerable people. We are still a long way from individuals being posted a test to find out if the symptoms they experienced some months ago were COVID-19 or another infection with similar symptoms, and from immunity passports.
“We are still waiting for longer-term studies that show how long people remain protected from reinfection, and that start to link antibody levels measured by different testing methods with such immunity.
“Another important point is addressed – whilst home testing can be more convenient than visiting a clinic or hospital to have a healthcare professional do a test, it raises the additional important challenge of usability. Without training and supervision, there is pressure on the individual at home to follow instructions correctly, under pressure, with possible reduction in accuracy. Whilst the study showed that a lot of people can use rapid tests at home, a subset of participants involved had difficulty with particular test components, and these home tests were clearly not perfect. An imperfect test can still be used for serosurveillance however, because the purpose of the testing is to survey populations – these results are still not useful for the individual.
“Overall, home antibody testing is clearly very useful but just one tool that complements other vital tools such as laboratory antibody tests (more accurate but harder to access) and the critical swab testing for virus ‘now’.”
Prof Liam Smeeth, Professor of Clinical Epidemiology, and Dean of the Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, said:
“This is a high quality study providing valuable findings. As the authors make clear, the tests used were able to provide useful surveillance data at the population level, but the tests are not accurate enough to be applied to individuals to guide their behaviour. A crucial uncertainty is that we still do not know the extent to which antibody levels indicate immunity from infection, or indicate whether people are able to carry and pass on the virus.
“The levels of exposure in different geographical areas and in different population groups are in line with the patterns of death from Covid-19. The high levels of exposure in care-home workers highlights the substantial risks these crucial workers are exposed to though their work, and emphasises the importance of protection and regular testing of this group in future efforts.”
Prof Rowland Kao, the Sir Timothy O’Shea Professor of Veterinary Epidemiology and Data Science, University of Edinburgh, said:
“This seroprevalence study provides us with the best picture yet of the circulation of infection in England. The results are not unexpected but do confirm a much higher circulation of COVID-19 than we see from looking at confirmed cases alone – about ten times as many, with almost a third of all testing positive reporting having experienced no symptoms. What we don’t know is how many of those without easily detectable symptoms may have contributed to circulation of infection – until we have better evidence the safest assumption to make is that they do present a risk of transmission. As contact with either a suspected or confirmed cases was a substantial risk factor for testing positive, the results highlight the importance of good contact tracing and the role that self-isolation is likely to play in controlling future outbreaks.”
Dr Simon Clarke, Associate Professor of Cellular Microbiology at the University of Reading, said:
“The finding that 6% of the population have antibodies against the coronavirus causing Covid-19, matches very closely with a smaller study published by the ONS in June. Antibodies are a very good marker for telling us how many people have had the infection, but their presence does not prove that someone is immune to re-infection. This study was conducted using test kits likened to pregnancy tests in the way they’re administered. While such tests currently aren’t accurate enough to reliably diagnose individual cases, they can be used to gain an overall picture of the prevalence of antibodies in a large number of people.
“At the beginning of the UK epidemic, it was estimated that approximately 60% of the population would need to be infected by this coronavirus for herd immunity to be acquired. These findings therefore imply that for that to happen, we would have needed to see a much greater level of community infection, perhaps a 10-fold increase, with correspondingly increased levels of illness and death.”
* Preprint (not a paper): ‘Antibody prevalence for SARS-CoV-2 following the peak of the pandemic in England: REACT2 study in 100,000 adult’ by Helen Ward et al. This work is not peer-reviewed
** Published papers:
‘Clinical and laboratory evaluation of SARS-CoV-2 lateral flow assays for use in a national COVID-19 seroprevalence survey’ by Barnaby Flower et al. was published in Thorax on Wednesday 12 August 2020.
DOI: 10.1136/thoraxjnl-2020-215732
https://thorax.bmj.com/content/early/2020/08/11/thoraxjnl-2020-215732
‘Usability and acceptability of home-based self-testing for SARS-CoV-2 antibodies for population surveillance’ by Christina Atchison et al. was published in Clinical Infectious Diseases on Wednesday 12 August 2020.
DOI: 10.1093/cid/ciaa1178
https://academic.oup.com/cid/advance-article/doi/10.1093/cid/ciaa1178/5891615
All material here: https://www.imperial.ac.uk/medicine/research-and-impact/groups/react-study/real-time-assessment-of-community-transmission-findings/
https://www.gov.uk/government/statistics/react-2-study-of-coronavirus-antibodies-june-2020-results
All our previous output on this subject can be seen at this weblink:
www.sciencemediacentre.org/tag/covid-19
Declared interests
Dr Alexander Edwards: “Dr Al Edwards has been involved in a separate crowdfunded study into usability of home testing: https://sites.reading.ac.uk/imagine/project/improving-covid19-testing/.”
None others received.