Risk assessment and seroprevalence of SARS-CoV-2 infection in healthcare workers of COVID-19 and non-COVID-19 hospitals in Southern Switzerland

Luca Piccoli; Paolo Ferrari; Giovanni Piumatti; Sandra Jovic; Blanca Fernandez Rodriguez; Federico Mele; Isabella Giacchetto-Sasselli; Tatiana Terrot; Chiara Silacci-Fregni; Elisabetta Cameroni; Stefano Jaconi; Nicole Sprugasci; Istvan Bartha; Davide Corti; Mariagrazia Uguccioni; Antonio Lanzavecchia; Christian Garzoni; Olivier Giannini; Enos Bernasconi; Luigia Elzi; Emiliano Albanese; Federica Sallusto; Alessandro Ceschi

doi:10.1016/j.lanepe.2020.100013

Risk assessment and seroprevalence of SARS-CoV-2 infection in healthcare workers of COVID-19 and non-COVID-19 hospitals in Southern Switzerland

Lancet Reg Health Eur. 2021 Feb:1:100013. doi: 10.1016/j.lanepe.2020.100013. Epub 2020 Dec 17.

Authors

Luca Piccoli¹, Paolo Ferrari^{2

3

4}, Giovanni Piumatti^{5

6}, Sandra Jovic⁷, Blanca Fernandez Rodriguez⁷, Federico Mele⁷, Isabella Giacchetto-Sasselli⁷, Tatiana Terrot⁸, Chiara Silacci-Fregni¹, Elisabetta Cameroni¹, Stefano Jaconi¹, Nicole Sprugasci¹, Istvan Bartha¹, Davide Corti¹, Mariagrazia Uguccioni^{7

9}, Antonio Lanzavecchia⁷, Christian Garzoni^{10

11}, Olivier Giannini^{2

3}, Enos Bernasconi², Luigia Elzi², Emiliano Albanese⁶, Federica Sallusto^{7

12}, Alessandro Ceschi^{3

8

13

14}

Affiliations

¹ Humabs BioMed SA, A Subsidiary of Vir Biotechnology, Bellinzona, Switzerland.
² Department of Internal Medicine, Ente Ospedaliero Cantonale, Bellinzona, Switzerland.
³ Faculty of Biomedical Sciences, Università della Svizzera italiana, Lugano, Switzerland.
⁴ Clinical School, University of New South Wales, Sydney, Australia.
⁵ Division of Primary Care, Population Epidemiology Unit, Geneva University Hospitals, Geneva, Switzerland.
⁶ nstitute of Public Health, Faculty of Biomedical Sciences, Università della Svizzera Italiana, Lugano, Switzerland.
⁷ Institute for Research in Biomedicine, Bellinzona, Università della Svizzera italiana, Bellinzona, Switzerland.
⁸ Clinical Trial Unit, Ente Ospedaliero Cantonale, Lugano, Switzerland.
⁹ Department of Biomedical Sciences, Humanitas University, Pieve Emanuele (Milan), Italy.
¹⁰ Clinic of Internal Medicine and Infectious Diseases, Clinica Luganese Moncucco, Lugano, Switzerland.
¹¹ Department of Infectious Diseases, Bern University Hospital, University of Bern, Bern, Switzerland.
¹² Institute of Microbiology, ETH Zurich, Zurich, Switzerland.
¹³ Division of Clinical Pharmacology and Toxicology, Institute of Pharmacological Sciences of Southern Switzerland, Ente Ospedaliero Cantonale, Lugano, Switzerland.
¹⁴ Department of Clinical Pharmacology and Toxicology, University Hospital Zurich, Zurich, Switzerland.

Abstract

Background: Hospital healthcare workers (HCW), in particular those involved in the clinical care of COVID-19 cases, are presumably exposed to a higher risk of acquiring the disease than the general population.

Methods: Between April 16 and 30, 2020 we conducted a prospective, SARS-CoV-2 seroprevalence study in HCWs in Southern Switzerland. Participants were hospital personnel with varying COVID-19 exposure risk depending on job function and working site. They provided personal information (including age, sex, occupation, and medical history) and self-reported COVID-19 symptoms. Odds ratio (OR) of seropositivity to IgG antibodies was estimated by univariate and multivariate logistic regressions.

Findings: Among 4726 participants, IgG antibodies to SARS-CoV-2 were detected in 9.6% of the HCWs. Seropositivity was higher among HCWs working on COVID-19 wards (14.1% (11.9-16.5)) compared to other hospital areas at medium (10.7% (7.6-14.6)) or low risk exposure (7.3% (6.4-8.3)). OR for high vs. medium wards risk exposure was 1.42 (0.91-2.22), P = 0.119, and 1.98 (1.55-2.53), P<0.001 for high vs. low wards risk exposure. The same was for true for doctors and nurses (10.1% (9.0-11.3)) compared to other employees at medium (7.1% (4.8-10.0)) or low risk exposure (6.6% (5.0-8.4)). OR for high vs. medium profession risk exposure was 1.37 (0.89-2.11), P = 0.149, and 1.75 (1.28-2.40), P = 0.001 for high vs. low profession risk exposure. Moreover, seropositivity was higher among HCWs who had household exposure to COVID-19 cases compared to those without (18.7% (15.3-22.5) vs. 7.7% (6.9-8.6), OR 2.80 (2.14-3.67), P<0.001).

Interpretation: SARS-CoV-2 antibodies are detectable in up to 10% of HCWs from acute care hospitals in a region with high incidence of COVID-19 in the weeks preceding the study. HCWs with exposure to COVID-19 patients have only a slightly higher absolute risk of seropositivity compared to those without, suggesting that the use of PPE and other measures aiming at reducing nosocomial viral transmission are effective. Household contact with known COVID-19 cases represents the highest risk of seropositivity.

Funding: Henry Krenter Foundation, Ente Ospedaliero Cantonale and Vir Biotechnology.

Keywords: COVID-19; Healthcare workers; Seroprevalence.