Non-occupational and occupational factors associated with specific SARS-CoV-2 antibodies among hospital workers – A multicentre cross-sectional study

Kahlert, Christian R.; Persi, Raphael; Güsewell, Sabine; Egger, Thomas; Leal-Neto, Onicio B.; Sumer, Johannes; Flury, Domenica; Brucher, Angela; Lemmenmeier, Eva; Möller, J. Carsten; Rieder, Philip; Stocker, Reto; Vuichard-Gysin, Danielle; Wiggli, Benedikt; Albrich, Werner C.; Flury, Baharak Babouee; Besold, Ulrike; Fehr, Jan; Kuster, Stefan P.; McGeer, Allison; Risch, Lorenz; Schlegel, Matthias; Friedl, Andrée; Vernazza, Pietro; Kohler, Philipp

OBJECTIVES: Protecting healthcare workers (HCW) from Coronavirus Disease-19 (COVID-19) is critical to preserve the functioning of healthcare systems. We therefore assessed seroprevalence and identified risk factors for Severe Acute Respiratory Syndrome-Coronavirus-2 (SARS-CoV-2) seropositivity in this population. METHODS: Between June 22(nd) and August 15(th) 2020, HCW from institutions in Northern/Eastern Switzerland were screened for SARS-CoV-2 antibodies. We recorded baseline characteristics, non-occupational and occupational risk factors. We used pairwise tests of associations and multivariable logistic regression to identify factors associated with seropositivity. RESULTS: Among 4’664 HCW from 23 healthcare facilities, 139 (3%) were seropositive. Non-occupational exposures independently associated with seropositivity were contact with a COVID-19-positive household (adjusted OR=59, 95%-CI: 33-106), stay in a COVID-19 hotspot (aOR=2.3, 95%-CI: 1.2-4.2), and male sex (aOR=1.9, 95%-CI: 1.1-3.1). Blood group 0 vs. non-0 (aOR=0.5, 95%-CI: 0.3-0.8), active smoking (aOR=0.4, 95%-CI: 0.2-0.7), living with children <12 years (aOR=0.3, 95%-CI: 0.2-0.6), and being a physician (aOR 0.2, 95%-CI: 0.1-0.5) were associated with decreased risk. Other occupational risk factors were close contact to COVID-19 patients (aOR=2.7, 95%-CI: 1.4-5.4), exposure to COVID-19-positive co-workers (aOR=1.9, 95%-CI: 1.1-2.9), poor knowledge of standard hygiene precautions (aOR=1.9, 95%-CI: 1.2-2.9), and frequent visits to the hospital canteen (aOR=2.3, 95%-CI: 1.4-3.8). CONCLUSIONS: Living with COVID-19-positive households showed the strongest association with SARS-CoV-2 seropositivity. We identified several potentially modifiable work-related risk factors, which might allow mitigation of the COVID-19 risk among HCW. The lower risk among those living with children, even after correction for multiple confounders, is remarkable and merits further study.