Seroprevalence to the SARS-CoV-2 virus among the population of the Republic of Belarus

Objective. Evaluation of the level of population immunity to SARS-CoV-2 among the population of the Republic of Belarus. Materials and methods . Evaluation of population immunity to SARS-CoV-2 among the population of the Republic of Belarus was carried out in accordance with the protocol developed by World Health Organization (WHO) and adapted for the Republic of Belarus («An age-stratified seroepidemiological investigation protocol for COVID-19 infection in the Republic of Belarus») within the 3-stage longitudinal stratified by age seroepidemiological study, which included questionnaires and a study of the seroprevalence to the RBD fragment of the SARS-CoV-2 S protein. Determination of total (IgM and IgG) antibodies to SARS-CoV-2 was carried out using the qualitative enzyme immunoassay kit Wantai SARS-CoV-2 Total Ab (Beijing Wantai Biological Pharmacy Enterprise, Beijing, China). Results. At the first stage of the study, conducted one year after the registration of the first COVID-19 case, the population immunity in the Republic of Belarus was 63.2%. The proportion of seropositive participants both among children and adults increased during the subsequent two stages, reaching a combined total of 81.0% by October 2021. Seroprevalence among participants with an active lifestyle was higher compared to individuals who limited physical contacts during this period. At all three stages of the study, the highest proportion of seropositive individuals was found among healthcare workers. Conclusion . Formation of the population immunity to the SARS-CoV-2 virus occurred through a hybrid pathway, combining natural protection following infection and post-vaccination immunity. The country’s COVID-19 response strategy, including the absence of lockdowns and a large-scale vaccination campaign, had a significant impact on the level of seroprevalence.