Study of the Level and Structure of Population Immunity to SARS-CoV2 in the Population of the Republic of Tatarstan during the Second Peak of the Spread of COVID-19

Background. The COVID-19 pandemic has become a serious challenge for all of humanity due to the rapid global spread, high frequency of severe forms, increased mortality and required the development of new approaches to managing epidemiological processes. Serological studies are the most important tool for monitoring the infectious process, identifying risk groups, assessing the effect of vaccines used and epidemiological projections.

Purpose. Conducting serological monitoring in relation to the modern transferred new coronavirus infection determining the level and structure of population immunity to SARS-CoV-2 in the population of the Republic of Tatarstan; maintaining the period of spread of COVID-19 from August to December 2020.

Materials and methods. The study involved 41 444 residents of the Republic of Tatarstan, who filled out questionnaires that included clinical, anamnestic data and an epidemiological history in relation to COVID-19, who were tested for the presence of common antibodies (IgG, IgA and IgM) to the SARS coronavirus. CoV-2 by the method of enhanced chemiluminescence on the VITROS 3600 analyzer using the VITROS Anti-SARS-CoV-2 Total Reagent Pack test systems.

Statistical processing was carried out by methods of variation statistics and correlation analysis according to the Pearson method using MS Excel and WinPepi.

Results. Seropositivity to SARSCoV-2 in the population of the Republic of Tatarstan averaged 35.8 ± 0.235%. An increase in the level of seropositive persons was noted from 29.95 ± 0.674% in August to 68 ± 9.33% in December. The highest proportion of seropositive individuals was found in was found in the group of the able-bodied population aged 18–59 years. The average geometric titer of antibodies was 4.2 (4.09–4.31), among seropositive – 89.29 (88.13–90.46). In the social and professional structure of the population, the largest proportion of seropositive individuals was found in was found among production workers 40.35 ± 2.177, creative professions – 40 ± 9.798; health care 35.24 ± 0.389; 34.26 ± 1.218 unemployed and 33.06 ± 2.479 civil servants. Among the residents of the Republic of Tatarstan, seropositive to the SARS-CoV-2 virus, the proportion of asymptomatic forms of infection was 82.59 ± 0.446%.

Сonclusions. There is a positive dynamics of seropositivity among the population of the Republic of Tatarstan. The results of sero-epidemiological monitoring can be used to predict the epidemiological situation, plan measures for specific and non-specific prophylaxis of COVID19.

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