Evaluation of the dynamics of changes in Covid-19 seroprevalence in various social groups during the SARS-COV-2 pandemic

Serological methods have become especially in demand during the SARS-CoV-2 pandemic, as they have high specificity, ease of implementation, good speed and relatively low cost.People with symptoms of COVID-19 were found to be statistically significantly more likely to test positive for IgM and IgG. The positivity coefficient was also significantly higher in the group of people with symptoms of coronavirus infection. The distribution of the density of positive ELISA results for all types of antibodies was multimodal in both groups of patients, with many peaks that differ both in density values and in time periods of their detection. When analyzing the multimodal distribution of the obtained seroprevalence results for the period from 06/01/2020 to 01/18/2022, it was found that in people at risk, peaks of increased density of positive for IgM results appeared earlier, which may reflect the initial spread of infection in asymptomatic patients. The smallest differences in the time of occurrence of peaks of high density of seropositive ELISA results between groups was determined for IgA — from 2 to 8 days. This may be due to the relatively short seroconversion time for this type of antibody. In general, using serological methods for diagnosing COVID-19, it is possible to assess the prevalence of coronavirus infection in different cohorts of the population, as well as to study in more detail the features of the immune response to SARS-CoV-2.