High seroprevalence of anti-SARS-CoV-2 antibodies among Ethiopian healthcare workers

  1. Tesfaye Gelanew
  2. Berhanu Seyoum
  3. Andargachew Mulu
  4. Adane Mihret
  5. Markos Abebe
  6. Liya Wassie
  7. Baye Gelaw
  8. Abebe Sorsa
  9. Yared Merid
  10. Yilkal Muchie
  11. Zelalem Teklemariam
  12. Bezalem Tesfaye
  13. Mahlet Osman
  14. Gutema Jebessa
  15. Abay Atinafu
  16. Tsegaye Hailu
  17. Antenehe Habte
  18. Dagaga Kenea
  19. Anteneh Gadisa
  20. Desalegn Admasu
  21. Emnet Tesfaye
  22. Timothy A. Bates
  23. Jote Tafese Bulcha
  24. Rea Tschopp
  25. Dareskedar Tsehay
  26. Kim Mullholand
  27. Rawleigh Howe
  28. Abebe Genetu
  29. Fikadu G. Tafesse
  30. Alemseged Abdissa

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Abstract

Background

COVID-19 pandemic has a devastating impact on the economies and health care system of sub-Saharan Africa. Healthcare workers (HWs), the main actors of the health system, are at higher risk because of their occupation. Serology-based estimates of SARS-CoV-2 infection among HWs represent a measure of HWs’ exposure to the virus and could be used as a guide to the prevalence of SARS-CoV-2 in the community and valuable in combating COVID-19. This information is currently lacking in Ethiopia and other African countries. This study aimed to develop an in-house antibody testing assay, assess the prevalence of SARS-CoV-2 antibodies among Ethiopian high-risk frontline HWs.

Methods

We developed and validated an in-house Enzyme-Linked Immunosorbent Assay (ELISA) for specific detection of anti-SARS-CoV-2 receptor binding domain immunoglobin G (IgG) antibodies. We then used this assay to assess the seroprevalence among HWs in five public hospitals located in different geographic regions of Ethiopia. From consenting HWs, blood samples were collected between December 2020 and February 2021, the period between the two peaks of COVID-19 in Ethiopia. Socio-demographic and clinical data were collected using questionnaire-based interviews. Descriptive statistics and bivariate and multivariate logistic regression were used to determine the overall and post-stratified seroprevalence and the association between seropositivity and potential risk factors.

Results

Our successfully developed in-house assay sensitivity was 100% in serum samples collected 2- weeks after the first onset of symptoms whereas its specificity in pre-COVID-19 pandemic sera was 97.7%. Using this assay, we analyzed a total of 1997 sera collected from HWs. Of 1997 HWs who provided a blood sample, and demographic and clinical data, 51.7% were females, 74.0% had no symptoms compatible with COVID-19, and 29.0% had a history of contact with suspected or confirmed patients with SARS-CoV-2 infection. The overall seroprevalence was 39.6%. The lowest (24.5%) and the highest (48.0%) seroprevalence rates were found in Hiwot Fana Specialized Hospital in Harar and ALERT Hospital in Addis Ababa, respectively. Of the 821 seropositive HWs, 224(27.3%) of them had a history of symptoms consistent with COVID-19 while 436 (> 53%) of them had no contact with COVID-19 cases as well as no history of COVID-19 like symptoms. A history of close contact with suspected/confirmed COVID-19 cases is associated with seropositivity (Adjusted Odds Ratio (AOR) = 1.4, 95% CI 1.1–1.8; p = 0.015).

Conclusion

High SARS-CoV-2 seroprevalence levels were observed in the five Ethiopian hospitals. These findings highlight the significant burden of asymptomatic infection in Ethiopia and may reflect the scale of transmission in the general population.

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  1. Version published to 10.1186/s12879-022-07247-z
  2. Version published to 10.21203/rs.3.rs-676935/v1 on Research Square
  3. ScreenIT

    SciScore for 10.1101/2021.07.01.21259687: (What is this?)

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

    Table 1: Rigor

    EthicsConsent: Ethical approvals were obtained from all institutions and written informed consent was obtained from each participant.
    Sex as a biological variablenot detected.
    RandomizationLtd) following the manufacturers’ instructions using randomly selected small panels (pre-pandemic; n=40, and COVID-19; n=40) from the large size panels that were used for our assay validation.
    Blindingnot detected.
    Power Analysisnot detected.
    Cell Line Authenticationnot detected.

    Table 2: Resources

    Antibodies
    SentencesResources
    The assay is an indirect ELISA, measuring serum IgG against RBD of spike protein SARS-CoV-2, using a horseradish peroxidase-linked anti-human IgG secondary antibody (Invitrogen, USA)
    anti-human IgG
    suggested: None
    Detection of RBD-specific IgG antibodies in each serum sample was done in duplicate microwells of ELISA plate.
    RBD-specific IgG
    suggested: None
    Positive and negative control samples were selected by matching their optical density (OD) readouts with WHO solidarity II plasma panels developed by the United Kingdom’s National Institute for Biological Standards and Control (NIBSC;20/130, single donor, high-titer antibody), 20/120 (single donor, relatively high-titer antibody), 20/122 (pool of five donor samples, mid-titer antibody), 20/124 (low S1, high-nucleocapsid protein antibody titer), 20/126 (low-titer antibody, 20/128, negative control).
    Control (NIBSC;20/130, single donor, high-titer
    suggested: None
    In-house IgG ELISA comparison with commercial anti-SARS-CoV-2 serologic assays: We further compared the relative sensitivity and specificity of our assay with commercially available SARS-CoV-2 antibody tests: one lateral flow assay (LFA) (Hangzhou Realy Tech Co., LTD) and one ELISA (Beijing Wantai Biological Pharmacy Enterprise Co.,
    anti-SARS-CoV-2
    suggested: None
    We then utilized this assay to estimate the seroprevalence of anti-SARS-CoV-2 spike protein RBD IgG antibodies among HWS.
    anti-SARS-CoV-2 spike protein RBD IgG
    suggested: None
    Experimental Models: Cell Lines
    SentencesResources
    The RBD protein was then expressed in EXPi293 cells using previous methods12.
    EXPi293
    suggested: RRID:CVCL_D615)
    Recombinant DNA
    SentencesResources
    Enzyme-Linked Immunosorbent Assay (ELISA): The SARS-CoV-2 spike protein Receptor Binding Domain (RBD)-containing plasmid construct was cloned as described previously12.
    RBD)-containing
    suggested: None
    Software and Algorithms
    SentencesResources
    Data analysis: The data were double entered into REDCap Database Version 8.11.
    REDCap
    suggested: (REDCap, RRID:SCR_003445)
    Following data verification and validation, analysis was done using STATA Version 15.0.
    STATA
    suggested: (Stata, RRID:SCR_012763)
    Figures were generated using GraphPad Prism Version 9.1.
    GraphPad Prism
    suggested: (GraphPad Prism, RRID:SCR_002798)

    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:
    Despite these strengths, our study has several limitations. First, all hospital staff were invited to take part in the study, and hence selection bias might have affected our results. Second, recall bias might have affected the responses to the history of symptoms compatible with COVID-19, and close contact with a confirmed COVID-19 case, and thereby contributed to the absence of a strong correlation between seropositivity and these covariates, albeit having close contact with COVID-19 case. Third, our findings are slightly affected by the accuracy of our assay, with a sensitivity of 100% in convalescent samples from RT-PCR conformed COVID-19 cases and specificity of 97.7% in pre-COVID-19 samples. However, even this slight overestimation of the apparent seroprevalence associated with the assay specificity is likely to be matched by the proportion of study participants who might be infected and yet not produce humoral immune responses at the time of blood sample collection. In conclusion, we developed an in-house IgG ELISA that meets the WHO requirements to be utilized for SARS-CoV-2 serosurveillance studies. This seroprevalence study revealed a remarkably high seroprevalence (40-48%) of SARS-CoV-2 among HWs in the five public hospitals; with slight differences amongst hospitals, except Hiwot Fana Specialized Hospital in which relatively lowest (24.5%) seroprevalence was found. We found no seroprevalence rate differences between front line HWs and administrative staff, indicat...

    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.

  4. Version published to 10.1101/2021.07.01.21259687v1 on medRxiv