ABSTRACT
Objective. To assess the dynamics of seroprevalence of anti-SARS-CoV-2 antibodies in the population of non-vaccinated people. Materials and methods. During two months of the last quarter of 2020 (before the start of mass vaccination against the coronavirus infection), we analyzed the dynamics of the level of total anti-SARS-CoV-2 IgG and level of virus-neutralizing IgG (anti-RBD/S1) in 806 unvaccinated people without clinical signs of the disease Results. Upon first examination, 16.0% of participants were found to have positive total anti-SARS-CoV-2 IgG, while 82.6% were negative and 1.4% had indeterminate result. During two months of the pandemic, seroprevalence increased by 23.7% (from 16.0% to 39.7%). The proportion of people with an indeterminate result remained the same (1.4%). The proportion of patients with asymptomatic COVID-19 who were initially IgG-positive but became negative in two months was 5.4%. Some individuals with positive total anti-SARS-CoV-2 IgG were found to have non-reactive anti-RBD antibodies that did not ensure neutralization of coronavirus (17.8% upon first and 10.6% upon second examination). © 2021, Dynasty Publishing House. All rights reserved.