SARS-CoV-2 Ig G among Healthcare Workers and the General Population

Milani, Gregorio P.; Bianchetti, Mario G.; Togni, Giuseppe; Schoenenberger, Andreas W.; Muggli, Franco

It is assumed that healthcare workers are at the highest risk to be infected by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, few data from healthcare workers who do not primarily take care of patients with SARS-CoV-2 infection support this assumption. We investigated the prevalence of immunoglobulin G (Ig G) against SARS-CoV-2 among healthcare workers who do not primarily take care of patients with SARS-CoV-2 infection and the general population in a well-defined geographical area. The first part of the study was conducted in May 2020 in Val Mesolcina (Southern Switzerland), a valley with ~8000 inhabitants. All healthcare workers were invited. All participants (n = 488) of the Swiss Longitudinal Cohort Study (SWICOS), a cohort representative of the general population, were also invited. Circulating Ig G against spike protein subunit 1 of SARS-CoV-2 were tested in each subject. Subjects with positive Ig G were tested again after 6 months. The condition of being a healthcare worker, rather than a part of the general population, was tested as a predictor of seroprevalence positivity by both simple and multiple (adjusted for age and sex) logistic regression. Eleven (2.6%) of the 423 SWICOS participants and 46 (16%) out of 289 healthcare workers were positive for antibodies against SARS-CoV-2. The seroprevalence OR was 7.01 (95% CI: 3.53–15.47) for healthcare workers as compared to SWICOS participants. After adjusting for age and gender, the seroprevalence OR was 5.13 (95% CI: 2.54–10.40). About three quarters of the subjects in the SWICOS (73%) and in healthcare (79%) group with a previous positive serology still presented positive Ig G against the SARS-CoV-2 after 6 months. The present seroprevalence data point out that the SARS-CoV-2 infection is seven times higher among healthcare workers than in the general population of Val Mesolcina. Efforts to effectively protect all the healthcare personnel are needed.