Introduction. Asymptomatic transmission of the coronavirus poses a significant threat to efforts to reduce the incidence of COVID-19. A specific humoral immune response against SARS-CoV-2 can be induced in most symptomatic cases and in asymptomatic carriers. Determining the pattern of antibody response to SARS-CoV-2 infection in children can provide important information for improving screening and targeted protection of population that continue to suffer from this pandemic. Aim. To determine the level of antibodies to SARS-CoV-2 in children during the COVID19 epidemic. Materials and methods. Serum samples from 254 clinic patients from 1 to 17 years old, with an average age of 9.7±0.3 years, were studied by random selection. The analysis was carried out in 2 groups of patients: patients who underwent COVID-19 in the period from January 2021 to March 2022 with a positive SARS-CoV-2 PCR result (n=36) and a control group of children who deny the disease (n=218). IgM and IgG were determined in blood serum samples by means of ELISA using the SARS CoV-2-IgM and SARS CoV-2-IgG quantitative diagnostic kits (Vector-Best, Novosibirsk, Russia). Results. In the group of children who did not have COVID-19, negative results were detected in 25.2% of cases. IgG antibodies specific to SARS-CoV-2 were detected in 74.8% of patients, of which a low level of virus-neutralizing activity was found in 15.6% of patients, an average level in 20.2% of cases, and a high level in 39.0% of cases. In the group of children who had the disease, a low level of virus-neutralizing activity was detected in 29.4%, an average level in 32.4%, and a high level of IgG antibodies to SARS-CoV-2 was detected in 38.2% of cases. In the group of children who underwent COVID-19, 77.8% of the disease proceeded with symptoms of acute respiratory viral infections, 22.2% had CT signs of pneumonia, and there were no significant differences in the levels of specific antibodies. In the group of children who underwent COVID-19, 77.8% of the disease proceeded with symptoms of acute respiratory viral infections, 22.2% had CT signs of pneumonia, and there were no significant differences in the levels of specific antibodies. Analysis of seroprevalence in dynamics after the disease showed that the highest level of antibodies persisted for 2-4 months. after an illness. Conclusion. The proportion of asymptomatic forms of infection among children and adolescents is quite high. These undocumented infections often go unrecognized due to mild or absence of symptoms and, depending on their contagiousness and number of contacts, may play a significant role in the transmission of SARS-CoV-2. The findings raise important questions that should be explored in further studies regarding the role of serological tests in assessing the true extent of SARS-CoV-2 exposure in pediatric populations, as well as monitoring the response and duration of SARS-CoV2 antibody-mediated immunity.
