Prevalence of Antibodies to SARS-CoV-2 Following Natural Infection and Vaccination in Irish Hospital Healthcare Workers: Changing Epidemiology as the Pandemic Progresses

  1. Niamh Allen
  2. Melissa Brady
  3. Una Ni Riain
  4. Niall Conlon
  5. Lisa Domegan
  6. Antonio Isidro Carrion Martin
  7. Cathal Walsh
  8. Lorraine Doherty
  9. Eibhlin Higgins
  10. Colm Kerr
  11. Colm Bergin
  12. Catherine Fleming

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Abstract

In October 2020 SARS-CoV-2 seroprevalence among hospital healthcare workers (HCW) of two Irish hospitals was 15 and 4. 1%, respectively. We compare seroprevalence in the same HCW population 6 months later, assess changes in risk factors for seropositivity with progression of the pandemic and serological response to vaccination.

Methods

All staff of both hospitals ( N = 9,038) were invited to participate in an online questionnaire and SARS-CoV-2 antibody testing in April 2021. We measured anti-nucleocapsid and anti-spike antibodies. Frequencies and percentages for positive SARS-CoV-2 antibodies were calculated and adjusted relative risks for participant characteristics were calculated using multivariable regression analysis.

Results

Five thousand and eighty-five HCW participated. Seroprevalence increased to 21 and 13%, respectively; 26% of infections were previously undiagnosed. Black ethnicity (aRR 1.7, 95% CI 1.3–2.2, p < 0.001), lower level of education (aRR 1.4 for secondary level education, 95% CI 1.1–1.8, p = 0.002), living with other HCW (aRR 1.2, 95% CI 1.0–1.4, p = 0.007) were significantly associated with seropositivity. Having direct patient contact also carried a significant risk being a healthcare assistant (aRR 1.8, 95% CI 1.3–2.3, p < 0.001), being a nurse (aRR 1.4, 95% CI 1.0–1.8, p = 0.022), daily contact with COVID-19 patients (aRR 1.4, 95% CI 1.1–1.7, p = 0.002), daily contact with patients without suspected or confirmed COVID-19 (aRR 1.3, 95% CI 1.1–1.5, p = 0.013). Breakthrough infection occurred in 23/4,111(0.6%) of fully vaccinated participants; all had anti-S antibodies.

Conclusion

The increase in seroprevalence reflects the magnitude of the third wave of the pandemic in Ireland. Genomic sequencing is needed to apportion risk to the workplace vs. the household/community. Concerted efforts are needed to mitigate risk factors due to ethnicity and lower level of education, even at this stage of the pandemic. The undiagnosed and breakthrough infections call for ongoing infection prevention and control measures and testing of HCW in the setting of close contact. Vaccinated HCW with confirmed infection should be actively assessed, including SARS-CoV-2 whole genome sequencing (WGS), serology testing and assessment of host determinants, to advance understanding of the reasons for breakthrough infection.

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  1. Version published to 10.3389/fmed.2021.758118
  2. ScreenIT

    SciScore for 10.1101/2021.11.04.21265921: (What is this?)

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

    Table 1: Rigor

    EthicsConsent: All staff members of both hospitals (N=9038) were invited to participate in an online self-administered consent process and online questionnaire, followed by blood sampling for SARS-CoV-2 antibody testing in April 2021, in the same manner as October 2020 (6).
    IRB: Ethical approval: Ethical approval was obtained from the National Research Ethics Committee (NREC) for COVID-19, Study Number 20-NREC.
    Sex as a biological variablenot detected.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.

    Table 2: Resources

    Antibodies
    SentencesResources
    Laboratory Methods: All samples were tested using the Roche Elecsys anti-SARS-CoV-2 and the Roche Elecsys anti-SARS-CoV-2 S immunoassays detecting total antibodies (including IgG) to the nucleocapsid and spike proteins of the SARS-CoV-2 virus, respectively (29).
    anti-SARS-CoV-2
    suggested: None
    anti-SARS-CoV-2 S immunoassays detecting total antibodies (including IgG
    suggested: None
    Participants with detectable anti-N antibodies were presumed to have had previous natural infection.
    anti-N
    suggested: None
    Participants were deemed seropositive (i.e. assumed to have had past infection with SARS-CoV-2) if they had detectable anti-N antibodies, or if they had detectable anti-S antibodies but had not been previously vaccinated.
    anti-S
    suggested: None
    Software and Algorithms
    SentencesResources
    All analysis was conducted in Stata 15.1 (StataCorp LCC. 2019. College Station, TX 77845: USA).
    StataCorp
    suggested: (Stata, RRID:SCR_012763)

    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: An explicit section about the limitations of the techniques employed in this study was not found. We encourage authors to address study limitations.

    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.
    • Thank you for including a protocol registration statement.

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

    About SciScore

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  3. Version published to 10.1101/2021.11.04.21265921v1 on medRxiv