Seroprevalence of SARS-CoV-2 Antibodies Among 925 Staff Members in an Urban Hospital Accepting COVID-19 Patients in Osaka Prefecture, Japan

Background: The subclinical severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection rate in hospitalsremains unclear. To evaluate the effectiveness of our hospital's nosocomial infection control, we conducted a serological survey of anti-SARS-CoV-2 immunoglobulin G (IgG) among staff at our hospital, which is treating coronavirus disease 2019 (COVID-19) patients. Methods: The study design was cross-sectional. We measured anti-SARS-CoV-2 IgG using a laboratory-based quantitative test (Abbott immunoassay), which has a sensitivity and specificity of 100% and 99.6%, respectively. To investigate factors associated with seropositivity, we obtained additional information from participants via an anonymous questionnaire. Findings: We invited 1133 staff members in our hospital, and 925 (82%) participated. The mean age of participants was 40.0±11.8 years, and most were women (80.0%). According to job title, there were 149 medical doctors or dentists (16.0%), 489 nurses (52.9%), 140 medical technologists (14.2%), 49 healthcare providers (5.3%), and 98 administrative staff (10.5%). The overall seroprevalence for anti-SARS-CoV-2 IgG was 0.43% (4/925), which was similar to the seroprevalence of 0.54% (16/2970) in the general population in Osaka during the same period according to a government survey conducted with the same assay. Seropositive rates did not significantly differ according to job title, exposure to suspected or confirmed COVID-19 patients, or any other investigated factors. Interpretation: The subclinical SARS-CoV-2 infection rate in our hospital was similar to that in the general population under our nosocomial infection control measures. Funding: Unrestricted research funds from the Department of Gastroenterology and Department of Internal Medicine, Diabetes Center, Toyonaka Municipal Hospital. Declaration of Interests: The authors have no conflicts of interest to declare. Ethics Approval Statement: The present study was conducted in accordance with the principles of the Declaration of Helsinki, and approval was obtained from the Institutional Review Board of Toyonaka Municipal Hospital (No. 2020-05-08). We obtained written informed consent from participants prior to the study.