ASSESSMENT OF INDICATORS OF SPECIFIC HUMORAL IMMUNE AGAINST COVID-19 IN CHILDREN DURING THE DISTRIBUTION OF A NEW CORONAVIRUS INFECTION IN THE IRKUTSK REGION (2020-2021)

Background. There are many aspects ofthe development ofimmunity to the SARSCoV-2virus, that remain poorly understood, like the influence ofage-relatedcharacteristics on the intensity ofimmunity andthe course ofthe disease. Studies ofthe state ofimmunity are widely used, mainly in the adults. But questions ofthe patho- andimmunogenesis in children remain unsolved. Determining the nature ofseroconversion of antibodies to SARS-CoV-2 in this age group is important information for serological monitoring for targeted immunoprophylaxis of the population and forecasting the epidemic situation in the region. The aim. Evaluation of the dynamics of seroprevalence of specific antibodies to SARS-CoV-2 in children of the Irkutsk region during the pandemic of a new coronavirus infection. Materialsandmethods. StudywasconductedamongthechildpopulationoftheIrkutskregion in the periodJune 2020- December 2021as partofthe Rospotrebnadzor projectto assess populationimmunity to SARS-CoV-2in the population oftheRussian Federation. The content ofantibodies to SARS-CoV-2was determinedby ELISAusing native commercial test systems. Results. Population immunity among the child population of the Irkutsk region was characterized by an upward trend from 7.8 % at stage 1 to 98.4 % at stage 6 ofthe study. IgGto SARS-CoV-2remainedin 72.8%andformedin 25.6%ofpreviously seronegativechildren. Antibodiesweredetectedin66.1%ofcasesandpersistedforup to 10-15 months after COVID-19 infection. The proportion of asymptomatic forms of infection among seropositive volunteers was 69.5 %, which determines the high intensity of the latent epidemic process. Conclusion. Thelevelofseroprevalencewas98.4%. Thecurrentresultsofserological monitoring serve as a scientific basis for adjusting the list andscope ofmanagement decisions on the organization of preventive anti-epidemic measures, including vaccination. © 2023 Voprosy Literatury. All rights reserved.

Peculiarities of Humoral Immunity Formation in Medical Institution Employees Recovered from or Vaccinated against COVID-19 in Irkutsk.

We performed a seroepidemiological survey of the level and structure of population immunity to SARS-CoV-2 among employees of medical institution in the Irkutsk region during the COVID-19 pandemic. Seroprevalence assessment was organized from May 2020 to April 2021. The level of antibodies to SARS-CoV-2 was measured by ELISA. It was found that 139 (46%) of 299 examined workers were seropositive, including 50 (36%) vaccinated against COVID-19, 75 (54%) patients diagnosed with COVID-19, and 14 (10%) asymptomatic cases of SARS-CoV-2. The results obtained should be taken into account when predicting the dynamics of the epidemic process and organizing preventive (antiepidemic) measures, including vaccination.

Population immunity to SARS-COV-2 virus in residents of the irkutsk region in the dynamics of the epidemic

Background. Currently, the COVID-19 pandemic in the world and in Russia remains the main event. In this regard, the study of the manifestations of the epidemic process of the new coronavirus infection COVID-19 and the patterns of its development are an urgent area of research. In the fight against this viral disease, an important role is assigned to the study of the development of population immunity to the SARSCoV-2 virus, which will make it possible to assess the dynamics of seroprevalence and the formation of post-infectious humoral immunity, forecasting the development of the epidemiological situation, elucidating the characteristics of the epidemic process, and will also contribute to planning activities for specific and non-specific prevention of the disease. The aim: to determine the dynamics of population immunity to SARS-CoV-2 among the population of the Irkutsk region during the COVID-19 pandemic. Materials and methods. As a part of the Rospotrebnadzor project of assessing population immunity to SARS-CoV-2 in the population of the Russian Federation, the research has being conducted among the population of the Irkutsk region in the periods from June 23, 2020 to July 19, 2020 (Stage 1), from September 16, 2020 to September 25, 2020 (Stage 2), from December 7, 2020 to December 18, 2020 (Stage 3) and from March 8, 2021 to March 14, 2021(Stage 4), taking into account the reacted one recommended by the WHO. The content of antibodies to SARS-CoV-2 was determined by ELISA using a set of tests for human serum or plasma for specific immunoglobulins of class G to the proteins of the SARS-CoV-2 coronavirus. The results. The research of the humoral immunity of volunteers shows that during the period of an epidemic rise in the incidence of COVID-19 in the Irkutsk region, a low level of seroprevalence was formed (Stage 1 - 5.8 ± 0.5 %, Stage 2 - 12.1 ± 0.7 %), and in conditions of a long-term maximum increase in the incidence rate - 25.9 ± 1.0 % (Stage 3) and 46.2 ± 1.2 % (Stage 4). A significant proportion (Stage 1 - 82.2 ± 3.2 %, Stage 2 - 86.1 ± 2.3 %) of asymptomatic forms of infection characterizes the high intensity of the latently developing epidemic process in the first two stages. High levels of IgG in reconvalescents of COVID-19 persisted for an average of 3 to 5 months. Conclusion. The results of assessing the population immunity to the SARS-CoV-2 virus in the population of the Irkutsk region indicate that the seroprevalence level at Stage 4 of the research was 46.2 %. After the disease, on average, 49.5 % of persons did not detect antibodies. The results obtained should be taken into account when organizing preventive measures, including vaccination, and predicting morbidity. © 2021 Scientific Centre for Family Health and Human Reproduction Problems. All Rights Reserved.

Dynamics of changes in population immunity to the SARS-CоV-2 virus in residents the Irkutsk region in the context of the COVID-19 pandemic

Background. The ongoing COVID-19 pandemic in the world and in Russia remains the main event in 2020. A comprehensive study of the patterns of development and manifestations of the epidemic process of the new coronavirus infection COVID-19 is an urgent line of research. One of the important aspects of the fight against COVID-19 is the study of population immunity to the SARS-CoV-2 virus in order to assess seroprevalence and the formation process of post-infectious humoral immunity to SARS-CoV-2, forecast the development of the epidemiological situation, identify the features of the epidemic process, as well as planning measures for specific and non-specific disease prevention. The aim of the research is to determine the level and structure of population immunity to SARS-CoV-2 among the humans of the Irkutsk region during the COVID-19 epidemic. Materials and methods. As part of the Rospotrebnadzor project to assess population immunity to SARS-CoV-2 in the population of the Russian Federation, research is being conducted among the population of the Irkutsk region in the periods from 06/23/2020 to 07/19/2020 (stage 1), from 09/16/2020 to 09/25/2020 (Stage 2) and from 12/07/2020 to 12/18/2020 (stage 3), taking into account the reacted one recommended by the WHO. The content of antibodies to SARS-CoV-2 was determined by ELISA using a set of tests for human serum or plasma for specific immunoglobulins of class G to the nucleocapsid of the SARS-CoV-2 virus produced by FBUN GNCPMiB Rospotrebnadzor (Obolensk). The results of a research of the humoral immunity of volunteers show that during the period of an epidemic rise in the incidence of COVID-19 in the Irkutsk region, a low level of seroprevalence was formed (stage 1 – 5.8 ± 0.5%, stage 2 – 12,1 ± 0,7%), and in conditions of a long-term maximum increase in the incidence rate ¬– 25,9±1,0% (stage 3). A significant proportion (stage 1 – 81,2±3,2%, stage 2 – 90.9 ±1,9%) of asymptomatic forms of infection characterize the high intensity of the latently developing epidemic process in the first two stages. High levels of IgG in reconvalescents of COVID-19 persisted for an average of 3 to 4.5 months. Conclusion. The results of assessing the population immunity to the SARS-CoV-2 virus in the population of the Irkutsk region indicate that the seroprevalence level at the 3rd stage of the research was 25.9%. After the disease, on average, 41.6% of persons did not detect antibodies. The results obtained should be taken into account when organizing preventive measures, including vaccination, and predicting morbidity. © 2021, Numikom. All rights reserved.

Experience in studying seroprevalence to SARS-CoV-2 virus in the population of the Irkutsk Region during COVID-19 outbreak

Objective of the seroepidemiological study was to determine the level and structure of herd immunity to SARS-CoV-2 among the population of the Irkutsk Region during the period of an increase in the incidence of COVID-19. Materials and methods. The content of antibodies to SARS-CoV-2 was determined by ELISA applying a reagent panel “ELISA anti-SARS-Cov-2 IgG” produced by the State Scientific Center of Applied Microbiology and Biotechnology (Obolensk). Results and discussion. The investigation has revealed that the herd immunity of the total population of Irkutsk Region amounted to 5.8 %. The greatest share of seropositive persons was among the children aged 14–17 (13.8 %) and 1–6 (11.8 %). It has been established that the risk of infection increases by 3.1 times in case of contact with COVID-19 patients. After exposure to COVID-19, antibodies were produced in 56.5 % of the cases. The share of asymptomatic forms among seropositive residents of the Irkutsk Region reached 81.2 %. Consequently, during the chosen period of increased COVID-19 incidence among the population of Irkutsk Region low level of seroprevalence was formed. A significant proportion of asymptomatic forms of infection characterize high intensity of the latently developing epidemic process. The results obtained can be used when organizing preventive measures, including vaccination, and for forecasting morbidity rates. © 2020 Russian Research Anti-Plague Institute. All rights reserved.