Seroprevalence of antibodies to SARS-CoV-2 in healthcare workers: a cross-sectional study

  1. Joseph E Ebinger
  2. Gregory J Botwin
  3. Christine M Albert
  4. Mona Alotaibi
  5. Moshe Arditi
  6. Anders H Berg
  7. Aleksandra Binek
  8. Patrick Botting
  9. Justyna Fert-Bober
  10. Jane C Figueiredo
  11. Jonathan D Grein
  12. Wohaib Hasan
  13. Mir Henglin
  14. Shehnaz K Hussain
  15. Mohit Jain
  16. Sandy Joung
  17. Michael Karin
  18. Elizabeth H Kim
  19. Dalin Li
  20. Yunxian Liu
  21. Eric Luong
  22. Dermot P B McGovern
  23. Akil Merchant
  24. Noah Merin
  25. Peggy B Miles
  26. Margo Minissian
  27. Trevor Trung Nguyen
  28. Koen Raedschelders
  29. Mohamad A Rashid
  30. Celine E Riera
  31. Richard V Riggs
  32. Sonia Sharma
  33. Sarah Sternbach
  34. Nancy Sun
  35. Warren G Tourtellotte
  36. Jennifer E Van Eyk
  37. Kimia Sobhani
  38. Jonathan G Braun
  39. Susan Cheng

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Abstract

We sought to determine the extent of SARS-CoV-2 seroprevalence and the factors associated with seroprevalence across a diverse cohort of healthcare workers.

Design

Observational cohort study of healthcare workers, including SARS-CoV-2 serology testing and participant questionnaires.

Settings

A multisite healthcare delivery system located in Los Angeles County.

Participants

A diverse and unselected population of adults (n=6062) employed in a multisite healthcare delivery system located in Los Angeles County, including individuals with direct patient contact and others with non-patient-oriented work functions.

Main outcomes

Using Bayesian and multivariate analyses, we estimated seroprevalence and factors associated with seropositivity and antibody levels, including pre-existing demographic and clinical characteristics; potential COVID-19 illness-related exposures; and symptoms consistent with COVID-19 infection.

Results

We observed a seroprevalence rate of 4.1%, with anosmia as the most prominently associated self-reported symptom (OR 11.04, p<0.001) in addition to fever (OR 2.02, p=0.002) and myalgias (OR 1.65, p=0.035). After adjusting for potential confounders, seroprevalence was also associated with Hispanic ethnicity (OR 1.98, p=0.001) and African-American race (OR 2.02, p=0.027) as well as contact with a COVID-19-diagnosed individual in the household (OR 5.73, p<0.001) or clinical work setting (OR 1.76, p=0.002). Importantly, African-American race and Hispanic ethnicity were associated with antibody positivity even after adjusting for personal COVID-19 diagnosis status, suggesting the contribution of unmeasured structural or societal factors.

Conclusion and relevance

The demographic factors associated with SARS-CoV-2 seroprevalence among our healthcare workers underscore the importance of exposure sources beyond the workplace. The size and diversity of our study population, combined with robust survey and modelling techniques, provide a vibrant picture of the demographic factors, exposures and symptoms that can identify individuals with susceptibility as well as potential to mount an immune response to COVID-19.

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  1. ScreenIT

    SciScore for 10.1101/2020.07.31.20163055: (What is this?)

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

    Table 1: Rigor

    Institutional Review Board StatementIRB: The study protocol was approved by the Cedars-Sinai institutional review board and all participants provided written informed consent.
    Consent: The study protocol was approved by the Cedars-Sinai institutional review board and all participants provided written informed consent.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.
    Sex as a biological variablenot detected.

    Table 2: Resources

    Antibodies
    SentencesResources
    All active employees (total N∼15,000) were invited to participate in the study by providing a peripheral venous blood sample for serology testing and completing an electronic survey of questions regarding past medical history, social history, and work environment in addition to Covid-19 related symptoms and exposures.8,9 For the current study, we included all participants who completed both SARS-CoV-2 antibody testing and electronic survey forms (N=6,062).
    SARS-CoV-2
    suggested: None
    10 The Abbott assay detects antibodies directed against the nucleocapsid (N) antigen of the SARS-CoV-2 virus, which assists with packaging the viral genome after replication, and achieves specificity for IgG by incorporating an anti-human IgG signal antibody.
    anti-human IgG
    suggested: None
    Software and Algorithms
    SentencesResources
    Serologic Assays: All participant biospecimens underwent serology testing by the Cedars-Sinai Department of Pathology and Laboratory Medicine using the Abbott Diagnostics SARS-CoV-2 IgG chemiluminescent microparticle immunoassay assay (Abbott Diagnostics, Abbott Park, IL) performed on an Abbott Diagnostics Architect ci16200 analyzer.
    Abbott
    suggested: (Abbott, RRID:SCR_010477)

    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:
    Several limitations of this study merit consideration. Of the employees actively employed at our multi-site institution, only a proportion of all eligible participants enrolled; nonetheless, the sample size of the cohort was large, diverse, and representative of the source sample.7 Our seroprevalence estimates were based on using a validated assay of only IgG antibodies; assays of IgM antibodies may offer complementary information in future studies. Data collected on medical history, exposures, and symptoms were all self-reported, similar to approaches used in prior studies. We were unable to completely verify prior Covid-19 illness using viral test results in part given lack of universally available testing for all individuals, particularly those with minimal to no symptoms. In conclusion, in a highly diverse population of healthcare workers, demographic factors associated with Covid-19 antibody positivity indicate potential factors outside of the workplace associated with SARS-CoV-2 exposure, although these do not appear related to the number of people or to the presence of children in the home. Further, while for dyspnea may be a marker of more severe disease among those with Covid-19, it’s presence alone does not indicate infection.

    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.

    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.

  2. Version published to 10.1136/bmjopen-2020-043584
  3. Version published to 10.1101/2020.07.31.20163055 on medRxiv