Study of features of humoral immune response to the new coronavirus infection COVID-19 among healthcare workers

Abstract

Relevance. Since the beginning of the epidemic in China, there have been reports of nosocomial cases of SARSCoV-2 infection, including among medical workers. Studies of the intensity of humoral immune response to the SARSCoV-2 virus among medical workers who are much more likely to have professional contact with COVID-19 patients than are of particular importance. The aim is to study the seroprevalence and features of the humoral immune response to SARS-CoV-2 among medical workers. Materials and methods. The study included 61 medical workers from a multidisciplinary hospital in Kazan, which was redesigned to provide medical care to patients with new coronavirus infection, using the method of random sampling. The control group consisted of 60 non-medical workers. For the determination of IgG, a solid-phase ELISA was used. Statistical processing of the results was carried out using MS Excel software. The error of the relative value (M±m) was calculated, and the 95% confidence interval of the frequency of occurrence. To assess the significance of differences, the Student’s test (t-test) was used for independent samples. Results. The proportion of those seropositive to SARS-CoV-2 in the study group was 45.9%, compared with 21.7% in the control group. Among medical workers seropositive to the SARS-CoV-2 virus, the proportion of asymptomatic forms was 18.5%, mild forms — 53.6%, moderate forms and severe forms 25%. Two forms of the formation of a humoral immune response among seropositive ones were revealed: the first is characterized by the gradual elimination of specific IgG antibodies to SARSCoV-2 after 8 weeks from the onset of the first symptoms of COVID-19, the second form is an increase in specific IgG to SARS-CoV-2 and a higher value of the coefficient level of IgM positivity to SARS-CoV-2 after 8–10 weeks from the onset of the first symptoms. The group of seropositive, “raising antibodies”, prevailed over the group of individuals “eliminating antibodies”. Among seropositive medical workers, two forms of the formation of a humoral immune response were revealed: synchronous with the parallel elimination of IgG and IgM antibodies and a parallel increase in IgG and IgM. Conclusion. The study of the level of humoral immunity to COVID-19 in medical workers is important in terms of planning both anti-epidemic measures and predicting the effectiveness of the response to vaccination to SARS-CoV-2.