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

Nishida, T.; Iwahashi, H.; Yamauchi, K.; Kinoshita, N.; Okauchi, Y.; Suzuki, N.; Inada, M.; Abe, K.

Background: The subclinical severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection rate in hospitals during the pandemic remains unclear. To evaluate the effectiveness of our hospital's current nosocomial infection control, we conducted a serological survey of the anti-SARS-CoV-2 antibody (immunoglobulin G) among the staff of our hospital, which is treating coronavirus disease 2019 (COVID-19) patients. Methods: The study design was cross-sectional. We measured anti-SARS-CoV-2 immunoglobulin G in the participants using a laboratory-based quantitative test (Abbott immunoassay), which has a sensitivity and specificity of 100% and 99.6%, respectively. To investigate the factors associated with seropositivity, we also obtained some information from the participants with an anonymous questionnaire. Results: We invited 1133 staff members in our hospital, and 925 (82%) participated. The mean age of the 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 prevalence of seropositivity for anti-SARS-CoV-2 IgG was 0.43% (4/925), which was similar to the control 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. Conclusion: The subclinical SARS-CoV-2 infection rate in our hospital was not higher than that in the general population under our nosocomial infection control measures.