Assessment of Herd Immunity to SARS-CoV-2 Virus among the Population of the Kyrgyz Republic during COVID-19 Pandemic

This paper presents the results of a three round seroepidemiological study of the population for SARS-CoV-2 virus antibodies presence. The aim of the study was to assess herd immunity in the population of the Kyrgyz Republic stratified by age, gender and region. Materials and methods . The material for the study was blood samples and personal data (questionnaire) of individuals, who agreed to participate in the study. Results and discussion . The results of the three rounds study indicated that the proportion of seroprevalent persons at the 1st round was 30.8% (95% CI 29.5-32.1), at the 2nd round 71.2% (95% CI 69.9-72.5), at the 3rd round 92.3% (95% CI 91.5-93.1). High herd immunity in the population was defined by short-term and low incidence in the fourth wave of the pandemic compared to the global indicators of the COVID-19 fourth wave. Uneven territorial distribution of seroprevalence was observed through all rounds of the study. All three rounds of the study were characterized by the lack of coronavirus infection symptoms in some of the seropositive individuals. Symptoms presence in seropositive individuals in the second and third rounds tended to decrease compared to the 1st round results in general. The percentage of SARS-CoV-2 virus seropositive individuals among children was lower versus the adult population. The share of seropositive samples was less for men compared to women. Paired sera examination, collected after 8-20 months, showed the decreased level of antibodies by 64.6% compared to those collected 1-2 months after the disease. At the same time, an increased level of antibodies was observed in 35.4% of individuals.