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

  1. Helen Ward
  2. Christina Atchison
  3. Matt Whitaker
  4. Christl A Donnelly
  5. Steven Riley
  6. Deborah Ashby
  7. Ara Darzi
  8. Wendy S Barclay
  9. Graham Cooke
  10. Paul Elliott
  11. for the REACT study team

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Abstract

Background

REACT-2 Study 5 is a population survey of the prevalence of SARS-CoV-2 antibodies in the community in England.

Methods

We contacted a random sample of the population by sending a letter to named individuals aged 18 or over from the NHS GP registrations list. We then sent respondents a lateral flow immunoassay (LFIA) kit for SARS-CoV-2 antibody self-testing and asked them to perform the test at home and complete a questionnaire, including reporting of their test result. Overall, 161,537 adults completed questionnaires and self-administered LFIA tests for IgG against SARS-CoV-2 between 27 October and 10 November 2020.

Results

The overall adjusted and weighted prevalence was 5.6% (95% CI 5.4-5.7). This was an increase from 4.4% (4.3-4.5) in round 3 (September), a relative increase of 26.9% (24.0-29.9).The largest increase by age was in the 18 to 24 year old age group, which increased (adjusted and weighted) from 6.7% (6.3-7.2) to 9.9% (9.3-10.4), and in students, (adjusted, unweighted) from 5.9% (4.8-7.1) to 12.1% (10.8-13.5). Prevalence increased most in Yorkshire and The Humber, from 3.4% (3.0-3.8) to 6.3% (5.9-6.8) and the North West from 4.5% (4.2-4.9) to 7.7% (7.2-8.1). In contrast, the prevalence in London was stable, at 9.5% (9.0-9.9) and 9.5% (9.1-10.0) in rounds 3 and 4 respectively. We found the highest prevalence in people of Bangladeshi 15.1% (10.9-20.5), Pakistani 13.9% (11.2-17.2) and African 13.5% (10.7-16.8) ethnicity, and lowest in those of white British ethnicity at 4.2% (4.0-4.3).

Interpretation

The second wave of infection in England is apparent in increasing antibody prevalence, particularly in younger people, students, and in the Northern Regions. By late October a large proportion of the population remained susceptible to SARS-CoV-2 infection in England based on naturally acquired immunity from the first and early second wave.

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    SciScore for 10.1101/2021.07.21.21260926: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    EthicsIRB: Confidence intervals for the changes in prevalence were calculated using a normal approximation to the sampling distribution of a difference in prevalences.[12] Data were analysed using the statistical package R version 4.0.0.[13] We obtained research ethics approval from the South Central-Berkshire B Research Ethics Committee (IRAS ID: 283787), and Medicines and Healthcare products Regulatory Agency approval for use of the LFIA for research purposes only.
    Sex as a biological variablenot detected.
    Randomization8] Briefly, we included non-overlapping community samples from the adult population 18 years and older, using a self-administered questionnaire and LFIA test at home (Table 1).[6,8] Invitations were sent to named individuals randomly selected from the National Health Service (NHS) patient list which includes anyone registered with a General Practitioner (primary care physician) in England, covering almost the entire population.
    Blindingnot detected.
    Power Analysisnot detected.

    Table 2: Resources

    Antibodies
    SentencesResources
    The sensitivity of finger-prick blood (self-read) for IgG antibodies was 84.4% (70.5, 93.5) in RT-PCR confirmed cases in healthcare workers, and specificity 98.6% (97.1, 99.4) in pre-pandemic sera.[
    IgG
    suggested: None

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    Our study has limitations. Participation bias may have been introduced from the lower response from ethnic minority groups and people in more deprived areas. Therefore, it is possible that our study is not fully representative of the population of England. However, we attempted to minimise this by correcting for differential response rates and differences in population characteristics introduced by our sampling strategy. An important limitation was the exclusion of children for regulatory reasons as the LFIA was approved for research use in adults only. Given that the highest antibody prevalence and increases were observed in students and younger adults, not sampling children, in particular those of secondary school-age, means that we were unable to better understand infection risk factors in the youngest age groups. We used at-home self-adminitered LFIAs which despite being a cost-effective solution to conducting large-scale surveillance studies are generally less sensitive than laboratory assays.[9] However, our comprehensive laboratory evaluation and usability studies of the selected LFIA found it’s performance to be acceptable, in terms of sensitivity and specificity in comparision to a “gold standard” ELISA test,[9] and feasible to use at-home by members of the public, in terms of usability of the LFIA kit and achieving a valid test result.[15] In summary, although we observed a significant decline in the SARS-CoV-2 antibody prevalence in the adult population in England ...

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

    Results from scite Reference Check: We found no unreliable references.

    About SciScore

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  2. Version published to 10.1101/2021.07.21.21260926v1 on medRxiv