Seroprevalence of SARS-CoV-2 antibodies in social housing areas in Denmark

  1. Kamille Fogh
  2. Alexandra R. R. Eriksen
  3. Rasmus B. Hasselbalch
  4. Emilie Sofie Kristensen
  5. Henning Bundgaard
  6. Susanne D. Nielsen
  7. Charlotte S. Jørgensen
  8. Bibi F. S. S. Scharff
  9. Christian Erikstrup
  10. Susanne G. Sækmose
  11. Dorte K. Holm
  12. Bitten Aagaard
  13. Jakob Norsk
  14. Pernille Brok Nielsen
  15. Jonas H. Kristensen
  16. Lars Østergaard
  17. Svend Ellermann-Eriksen
  18. Berit Andersen
  19. Henrik Nielsen
  20. Isik S. Johansen
  21. Lothar Wiese
  22. Lone Simonsen
  23. Thea K. Fischer
  24. Fredrik Folke
  25. Freddy Lippert
  26. Sisse R. Ostrowski
  27. Steen Ethelberg
  28. Anders Koch
  29. Anne-Marie Vangsted
  30. Tyra Grove Krause
  31. Anders Fomsgaard
  32. Claus Nielsen
  33. Henrik Ullum
  34. Robert Skov
  35. Kasper Iversen

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Abstract

Background

COVID-19 is thought to be more prevalent among ethnic minorities and individuals with low socioeconomic status. We aimed to investigate the prevalence of SARS-CoV-2 antibodies during the COVID-19 pandemic among citizens 15 years or older in Denmark living in social housing (SH) areas.

Methods

We conducted a study between January 8th and January 31st, 2021 with recruitment in 13 selected SH areas. Participants were offered a point-of-care rapid SARS-CoV-2 IgM and IgG antibody test and a questionnaire concerning risk factors associated with COVID-19. As a proxy for the general Danish population we accessed data on seroprevalence from Danish blood donors (total Ig ELISA assay) in same time period.

Results

Of the 13,279 included participants, 2296 (17.3%) were seropositive (mean age 46.6 (SD 16.4) years, 54.2% female), which was 3 times higher than in the general Danish population (mean age 41.7 (SD 14.1) years, 48.5% female) in the same period (5.8%, risk ratios (RR) 2.96, 95% CI 2.78–3.16, p > 0.001). Seropositivity was higher among males (RR 1.1, 95% CI 1.05–1.22%, p = 0.001) and increased with age, with an OR seropositivity of 1.03 for each 10-year increase in age (95% CI 1.00–1.06, p = 0.031). Close contact with COVID-19-infected individuals was associated with a higher risk of infection, especially among household members (OR 5.0, 95% CI 4.1–6.2 p < 0,001). Living at least four people in a household significantly increased the OR of seropositivity (OR 1.3, 95% CI 1.0–1.6, p = 0.02) as did living in a multi-generational household (OR 1.3 per generation, 95% CI 1.1–1.6, p = 0.003). Only 1.6% of participants reported not following any of the national COVID-19 recommendations.

Conclusions

Danish citizens living in SH areas of low socioeconomic status had a three times higher SARS-CoV-2 seroprevalence compared to the general Danish population. The seroprevalence was significantly higher in males and increased slightly with age. Living in multiple generations households or in households of more than four persons was a strong risk factor for being seropositive. Results of this study can be used for future consideration of the need for preventive measures in the populations living in SH areas.

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  1. Version published to 10.1186/s12879-022-07102-1
  2. ScreenIT

    SciScore for 10.1101/2021.05.07.21256725: (What is this?)

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

    Table 1: Rigor

    EthicsIRB: Approvals and registrations: This study was performed as a national cross-sectional surveillance study under the authority task of Statens Serum Institut (SSI, Copenhagen, Denmark; which performs the epidemiological surveillance of infectious diseases for the Danish government) and according to Danish law does not require any formal approval from an ethics committee.
    Sex as a biological variablenot detected.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.

    Table 2: Resources

    Antibodies
    SentencesResources
    Detection of SARS CoV-2 antibodies: The OnSite COVID-19 IgG/IgM Rapid Test (CTK Biotech inc., Poway, California, United States of America) is a single use lateral flow chromatographic immunoassay for qualitative detection and differentiation of IgG and IgM antibodies to SARS-CoV-2 in whole blood, which yields results in 15 minutes.
    IgM
    suggested: None
    Participants were categorized as seropositive if they had developed IgG and/or IgM anti-SARS-CoV-2 antibodies.
    anti-SARS-CoV-2
    suggested: None
    Software and Algorithms
    SentencesResources
    All personal data obtained in REDCap was kept in accordance with the general data protection regulation and data protection law stated by the Danish Data Protection Agency.
    REDCap
    suggested: (REDCap, RRID:SCR_003445)

    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:
    Strengths and limitations: Our study has several limitations. The study design does not provide information on the point of time when participants became seropositive nor determination of time of infection. It is possible that participants who had been detected with COVID-19 earlier (viral throat-or nasopharyngeal swab or antibody test) or experienced COVID-19 like symptoms did not participate, leading to an underestimation of the seroprevalence and an potential overestimation of participants concerned about prior infection. Seropositivity can be underestimated due to the fact that antibodies in response to SARS-CoV-2 infection can first be detected about one week after symptom onset (22, 26). Seropositivity of Danish blood donors in the same period was used as a proxy for the general population with some limitations to consider. Blood donors were in the age group 17-70 years and our study group are in the age group 15-83 years. Seroprevalence in blood donors is determined on the basis of ELISA and not POCT. In general, blood donors are in good health, why seropositivity in this group could be lower than expected. There is a tendency for health care professionals to be overrepresented as blood donors, and this group is found to have a higher risk of SARS-CoV-2 infection (13), why the seropositivity of blood donors could be higher than expected.Participants did not have to document a residential address in the SH areas, why there may be participants from other areas. There is ...

    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

    SciScore is an automated tool that is designed to assist expert reviewers by finding and presenting formulaic information scattered throughout a paper in a standard, easy to digest format. SciScore checks for the presence and correctness of RRIDs (research resource identifiers), and for rigor criteria such as sex and investigator blinding. For details on the theoretical underpinning of rigor criteria and the tools shown here, including references cited, please follow this link.

  3. Version published to 10.1101/2021.05.07.21256725v1 on medRxiv