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SARS-CoV-2 seroprevalence and asymptomatic viral carriage in healthcare workers: a cross-sectional study
  1. Adrian Shields1,2,
  2. Sian E Faustini1,
  3. Marisol Perez-Toledo3,
  4. Sian Jossi3,
  5. Erin Aldera4,
  6. Joel D Allen5,
  7. Saly Al-Taei1,
  8. Claire Backhouse1,
  9. Andrew Bosworth2,
  10. Lyndsey A Dunbar1,
  11. Daniel Ebanks1,
  12. Beena Emmanuel1,
  13. Mark Garvey2,4,
  14. Joanna Gray2,
  15. I Michael Kidd6,
  16. Golaleh McGinnell2,
  17. Dee E McLoughlin7,
  18. Gabriella Morley7,
  19. Joanna O'Neill2,
  20. Danai Papakonstantinou4,
  21. Oliver Pickles8,
  22. Charlotte Poxon8,
  23. Megan Richter1,
  24. Eloise M Walker4,
  25. Kasun Wanigasooriya8,
  26. Yasunori Watanabe5,9,
  27. Celina Whalley8,
  28. Agnieszka E Zielinska4,
  29. Max Crispin5,
  30. David C Wraith3,10,
  31. Andrew D Beggs8,
  32. Adam F Cunningham3,
  33. Mark T Drayson1,10,
  34. Alex G Richter1,2
  1. 1 Clinical Immunology Service, University of Birmingham College of Medical and Dental Sciences, Birmingham, UK
  2. 2 University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK
  3. 3 Institute of Immunology and Immunotherapy, University of Birmingham, Birmingham, UK
  4. 4 Institute of Microbiology and Infection, University of Birmingham, Birmingham, UK
  5. 5 School of Biological Sciences, University of Southampton, Southampton, UK
  6. 6 Public Health England Midlands and East Region, Birmingham, UK
  7. 7 Institute of Inflammation and Ageing, University of Birmingham, Birmingham, UK
  8. 8 Surgical Research Laboratory, Institute of Cancer and Genomic Sciences, University of Birmingham, Birmingham, UK
  9. 9 Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford, UK
  10. 10 University Hospitals Birmingham NHS Foundation Trust and University of Birmingham, NIHR Biomedical Research Centre, Birmingham, UK
  1. Correspondence to Professor Alex G Richter, Clinical Immunology Service, University of Birmingham College of Medical and Dental Sciences, Birmingham B15 2TT, UK; a.g.richter{at}


Objective To determine the rates of asymptomatic viral carriage and seroprevalence of SARS-CoV-2 antibodies in healthcare workers.

Design A cross-sectional study of asymptomatic healthcare workers undertaken on 24/25 April 2020.

Setting University Hospitals Birmingham NHS Foundation Trust (UHBFT), UK.

Participants 545 asymptomatic healthcare workers were recruited while at work. Participants were invited to participate via the UHBFT social media. Exclusion criteria included current symptoms consistent with COVID-19. No potential participants were excluded.

Intervention Participants volunteered a nasopharyngeal swab and a venous blood sample that were tested for SARS-CoV-2 RNA and anti-SARS-CoV-2 spike glycoprotein antibodies, respectively. Results were interpreted in the context of prior illnesses and the hospital departments in which participants worked.

Main outcome measure Proportion of participants demonstrating infection and positive SARS-CoV-2 serology.

Results The point prevalence of SARS-CoV-2 viral carriage was 2.4% (n=13/545). The overall seroprevalence of SARS-CoV-2 antibodies was 24.4% (n=126/516). Participants who reported prior symptomatic illness had higher seroprevalence (37.5% vs 17.1%, χ2=21.1034, p<0.0001) and quantitatively greater antibody responses than those who had remained asymptomatic. Seroprevalence was greatest among those working in housekeeping (34.5%), acute medicine (33.3%) and general internal medicine (30.3%), with lower rates observed in participants working in intensive care (14.8%). BAME (Black, Asian and minority ethnic) ethnicity was associated with a significantly increased risk of seropositivity (OR: 1.92, 95% CI 1.14 to 3.23, p=0.01). Working on the intensive care unit was associated with a significantly lower risk of seropositivity compared with working in other areas of the hospital (OR: 0.28, 95% CI 0.09 to 0.78, p=0.02).

Conclusions and relevance We identify differences in the occupational risk of exposure to SARS-CoV-2 between hospital departments and confirm asymptomatic seroconversion occurs in healthcare workers. Further investigation of these observations is required to inform future infection control and occupational health practices.

  • viral infection
  • infection control
  • clinical epidemiology
  • respiratory infection

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See:

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  • Twitter @immunologydoc, @drmarkgarvey, @cameron_wraith, @AlexRichter3

  • Contributors AS helped conceive the study, collated and analysed the data, produced the figures, and wrote and revised the manuscript. SEF helped conceive the study, performed the experiments, and collated and analysed the data. MP-T and SJ performed the experiments, and collated and analysed the data. JDA, YW and MC produced the original trimeric spike-glycoprotein on which the serological assays are based and advised on methodology. JG, GoM and JON recruited participants to the study, facilitated the acquisition of clinical samples and collated the study results. MG collated and interpreted trust-level data on infections within UHBFT inpatients. IMK, AB and ADB supported the establishment and validation of the PCR workflow at the University of Birmingham. EA, DEM, GaM, DP, EMW and AEZ facilitated the establishment of RNA extraction and viral inactivation workflow within the category 3 biosafety laboratory at the University of Birmingham. KW, OP, CP and CW undertook PCR assays for the study. SA-T, CB, LAD, DE, BE and MR processed the samples, undertook the experiments and collated the results for serological studies. DCW, AFC and MTD helped conceive the study and supervised the analysis of data from the study. AGR is the senior and corresponding author for this manuscript and provided overall leadership for all aspects of the study. All authors helped revise the manuscript for publication.

  • Funding This study was funded internally by the University of Birmingham and University Hospitals Birmingham NHS Foundation Trust and carried out at the National Institute for Health Research (NIHR)/Wellcome Trust Birmingham Clinical Research Facility. This paper presents independent research supported by the NIHR Birmingham Biomedical Research Centre at the University Hospitals Birmingham NHS Foundation Trust and the University of Birmingham. Laboratory studies were undertaken by the Clinical Immunology Service, University of Birmingham. Work in MC’s laboratory was funded by the International AIDS Vaccine Initiative, Bill and Melinda Gates Foundation through the Collaboration for AIDS Vaccine Discovery (OPP1084519 and OPP1115782), the Scripps Consortium for HIV Vaccine Development (CHAVD) (AI144462), and the University of Southampton Coronavirus Response Fund which has over 1000 donors from around the world. ADB is currently supported by a Cancer Research UK Advanced Clinician Scientist award (C31641/A23923) and his laboratory is supported by CRUK Centre Birmingham (C17422/A25154) and the Birmingham Experimental Cancer Medicine Centre (C11497/A25127).

  • Disclaimer The views expressed are those of the authors(s) and not necessarily those of the NHS, the NIHR or the Department of Health.

  • Competing interests MTD reports personal fees from Abingdon Health, outside the submitted work. All other authors declare no competing interests.

  • Patient consent for publication Not required.

  • Ethics approval The study was approved by the London - Camden and Kings Cross Research Ethics Committee (reference 20/HRA/1817).

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement Data are available upon reasonable request. Proposals should be directed to the corresponding author.

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