The Study of Humoral Immunity in Healthсare Workers Exposed to COVID-19 Patients

Abstract

Introduction: Today, the novel coronavirus disease (hereinafter referred to as COVID-19) is spreading very quickly, and the healthcare workers exposed to COVID-19 patients represent the most vulnerable occupational cohort at risk of this contagious disease. Issues of immunological protection and health monitoring in medical personnel are of special interest and importance during the pandemic. The objective of our study was to assess humoral immunity in healthcare professionals by the presence of class G (IgG) antibodies to the nucleocapsid protein of SARS-CoV-2. Methods: We selected 345 healthcare workers of different specialties who might have been exposed to COVID-19 patients in hospitals and 72 age- and sex-matched controls (engineers, IT-personnel, and accountants) working elsewhere. Blood immunoglobulins G to the nucleocapsid protein of SARS-CoV-2 were tested by enzyme immunoassay using the commercial test kit produced by the Scientific Center for Applied Microbiology and Biotechnology, Obolensk, Russian Federation. The presence of IgG antibodies was established by the SARS-CoV-2 IgG antibody response index (index of positivity) calculated as the ratio of the optical density of the sample to the cut-off level of the assay. Results: The average IgG antibody response index value was significantly higher in the healthcare workers compared to the controls (p < 0.05). IgG antibodies to SARS-CoV-2 were more prevalent in nurses than in physicians (42.2 ± 3.6 % vs 31.0 ± 3.7 %, p < 0.05) and controls (42.2 ± 3.6 % vs 27.8 ± 5.3 %, p < 0.05) and their index values were higher than in the comparison group (p < 0.05). Conclusion: Our findings demonstrate a high prevalence of diagnostically important SARS-CoV-2 IgG antibody response and higher index values in nurses possibly related to prolonged contacts with COVID-19 patients. IgG antibodies found in 37.1 ± 2.6 % of the healthcare workers may be a consequence of both symptomatic and asymptomatic diseases and requires further study. According to the generally accepted opinion about the mechanisms of immune response to viral infections, we could assume the presence of protective immunity against COVID-19, but this issue requires further investigation. In the current epidemic situation, however, detection of IgG antibodies to SARS-CoV-2 can be used for implementation of preventive strategies among healthcare workers.