SARS-CoV-2 seroprevalence and asymptomatic viral carriage in healthcare workers: a cross-sectional study

Research output: Contribution to journalArticlepeer-review


External organisations

  • University of Southampton
  • University Hospitals Birmingham NHS Foundation Trust
  • College of Medical and Dental Sciences, The University of Birmingham
  • Public Health England Midlands and East Region


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.


Original languageEnglish
Pages (from-to)1089-1094
Number of pages6
Issue number12
Early online date11 Sep 2020
Publication statusPublished - 16 Nov 2020


  • Adult, Antibodies, Viral/blood, Asymptomatic Diseases, COVID-19/diagnosis, Cross-Sectional Studies, Female, Health Personnel/statistics & numerical data, Humans, Male, Middle Aged, Pandemics, RNA, Viral/analysis, SARS-CoV-2/genetics, Seroepidemiologic Studies