ABSTRACT
The global community is experiencing one of the largest infectious disease outbreaks in the 21st century. In the Saratov Region, the first case of new coronavirus infection was confirmed on March 19, 2020.The maximum increase in cases was noted between May 15 and June 30, during that time the total number of infected people in the region increased from 1526 to 6444. Since July 2020, a stable incidence level of new coronavirus infection has been observed in the Saratov Region, without a steady decline. The aim of the study was to assess the status of population immunity to the SARS-CoV-2 virus among residents of Saratov and the Saratov Region under the COVID-19 epidemic. Materials and methods. In the period from June 23 to July 26, 2020, a serological study of blood samples from 3372 volunteers of different age groups was conducted. The content of antibodies to SARS-CoV-2 was determined by ELISA using a set of reagents “ELISA anti-SARS-CoV-2 IgG” produced by the State Scientific Center of Applied Microbiology and Biotechnology of the Rospotrebnadzor (Russia). Results and discussion. In general, the incidence of COVID-19 in the Saratov Region is taking place against the background of moderate seroprevalence to the SARS-CoV-2 virus, accompanied by a high incidence of non-apparent (asymptomatic) forms of the infectious process. The absence of clinical symptoms of the disease, in the context of the limited use of methods for determining the RNA of the SARS-CoV-2 virus in PCR (11 % of the region’s population) makes it difficult to assess the real spread of the virus in the population and to establish the timing of the formation of persistent herd immunity. A low rate of antibody response among individuals with a positive result of PCR analysis, as well as among volunteers who had an infection in May, June 2020, indicates a weak formation of the immune response, or the prevalence of individuals reacting mainly by activating the cellular link of the immune system in the population. The obtained results, although they need to be explained in a number of respects, can be applied to the organization of preventive measures, including vaccination, in the region. © 2020 Russian Research Anti-Plague Institute. All rights reserved.
ABSTRACT
In late 2019, there were reports of an outbreak of infection caused by a new strain of beta coronavirus SARSCoV-2, the WHO identified the disease as coronavirus disease 2019 (COVID-19). In Tatarstan, the first case of COVID-19 was diagnosed on March 16, 2020, it was an imported case from France. The period of increase in the incidence lasted during the 12th to the 19th week, when the highest rate was recorded, amounting to 16.7 per 100 thousand population. Subsequently, a statistically significant decrease in the incidence was noted. Seroprevalence study was conducted at week 27 (8th week of decline of morbidity).The purpose of the seroepidemiological study was to measure the level and to identify the structure of herd immunity against the SARS-CoV-2 virus among the population of the Republic of Tatarstan during the rapid spread of the COVID-19 outbreak.Materials and methods. The selection of volunteers for the study was carried out by the method of questionnaires and randomization by random sampling. The exclusion criterion was active COVID-19 infection at the time of the survey. 2,946 people were examined for the presence of specific antibodies to SARS-CoV-2. The age of the surveyed volunteers ranged from 1 year to 70 years and older.Results. The results of the study showed that in the Republic of Tatarstan during the period of COVID-19 incidence, there was a moderate seroprevalence to SARS-CoV-2, which amounted to 31.3%, against the background of a high frequency (94.5%) of asymptomatic infection in seropositive individuals who did not have a history of past COVID-19 disease, positive PCR result and ARVI symptoms on the day of the examination. The maximum indicators of herd immunity were established in children aged 7-13 years (42.0%), children 14-17 years old (40.3%), with a simultaneous decrease in seroprevalence in persons aged 70 and older (24.0%). In different regions of the Republic of Tatarstan, there was a wide variation in seropositivity results from the minimum in the Zainsky district (8.6%) to the maximum in the Arsky district (74.3%). In 21 out of 38 surveyed districts, the results were unrepresentative due to the small sample size. In COVID-19 convalescents, antibodies are produced in 83.3% of cases. In persons with a positive result of the PCR analysis carried out earlier, antibodies were detected in 100% of cases. Among the volunteers who had contact with patients with COVID-19, the proportion of seropositive is 37%Conclusion. The dynamics of seroprevalence among the population of the Republic of Tatarstan can be qualified as positive, the results obtained can be used to develop a forecast for the development of the epidemiological situation, as well as to plan measures for specific and non-specific prevention of COVID-19. В конце 2019 г. появились сообщения о вспышке инфекции, вызванной новым штаммом beta-коронавируса SARS-CoV-2, заболевание ВОЗ определила как coronavirus disease 2019 (COVID-19). В Республике Татарстране первый случай COVID-19 был диагностирован 16.03.2020 г., это был завозной случай из Франции. Период нарастания заболеваемости продолжался с 12-й по 19-ю неделю, когда был зарегистрирован самый высокий показатель, составивший 16,7 на 100 тыс. населения. В дальнейшем отмечалось статистически значимое снижение заболеваемости. Исследование серопревалентности было проведено на 27-й неделе (8-я неделя снижения заболеваемости)Целью проведенного сероэпидемиологического исследования было определение уровня и структуры популяционного иммунитета к вирусу SARS-CoV-2 среди населения Республики Татарстан в период распространения COVID-19.Материалы и методы. Отбор волонтеров для исследования проводили методом анкетирования и рандомизации путем случайной выборки. Критерием исключения была активная инфекция COVID-19 в момент анкетирования. На наличие специфических антител к SARS-CoV-2 обследовано 2946 человек. Возраст обследованных добровольцев варьировал от 1 года до 70 лет и старше.Результаты. Результаты исследования показали, что в Республике Татарстан в период заболеваемости COVID-19 наблюдалась умеренная серопревалентность к SARS-CoV-2, составившая 31,3%, на фоне высокой частоты (94,5%) бессимптомной инфекции у серопозитивных лиц, не имевших в анамнезе перенесенного заболевания COVID-19, положительного результата ПЦР и симптомов ОРВИ в день обследования. Максимальные показатели коллективного иммунитета установлены у детей 7-13 лет (42,0%), детей 14-17 лет (40,3%) при одновременном снижении серопревалентности у лиц в возрасте 70 лет и старше (24,0%). В разных регионах Республики Татарстан наблюдалось широкое варьирование показателей серопозитивности от минимального в Заинском районе (8,6%) до максимального в Арском районе (74,3%). В 21 районе из 38 обследованных результаты были нерепрезентативны из-за малого числа наблюдений. У реконвалесцентов COVID-19 антитела вырабатываются в 83,3% случаев. У лиц с позитивным результатом ПЦР-анализа, проведенного ранее, антитела выявлялись в 100% случаев. Среди волонтеров, имевших контакты с больными COVID-19, доля серопревалентных 37%.Вывод. Динамику серопревалентности среди населения Республики Татарстан можно квалифицировать как позитивную. Полученные результаты могут быть использованы для разработки прогноза развития эпидемиологической ситуации, а также планирования мероприятий по специфической и неспецифической профилактике COVID-19.
ABSTRACT
Introduction. The COVID-19 pandemic was announced by WHO in February 2020. In the Kaliningrad region, the first case (imported) was registered in early March 2020, the beginning of the epidemic increase fell on the 14th week. 2020, and the peak incidence was reached in the 22nd week of the year, after which there was a steady decrease in the number of cases. The study of population immunity was carried out at the 32nd week during the period of the lowest level of intensity of the epidemic process. Purpose of the study. Assessment of the assessment of the level of population immunity to the SARS-CoV-2 virus among the population of the Kaliningrad region during the period of the epidemic incidence of the population of COVID-19. Materials and methods. The study was carried out as part of the first stage of the Rospotrebnadzor program to assess population immunity to SARS-CoV-2 among the population of the Russian Federation. The selection of volunteers for the study was carried out by a questionnaire survey and subsequent randomization. The analysis includes the results of a survey of 2675 people. The number of volunteers in age groups ranged from 314 to 493 people. The results obtained were processed by the methods of variation statistics. Results. The results obtained showed that the average seroprevalence in the population was 50.2%, while the highest seroprevalence was found in the child age group 1-17 years (66.9%) and among persons aged 18-29 (57.0). No significant gender differences were found (men – 48,3 ± 1,6%, women – 51,1 ± 1,1%). The distribution of the proportion of seropositive people in the settlements of the region varied from 33,9% to 59.6%. The largest share of seroprevalence in the representative samples was found among people engaged in art / creativity (55,3%), the smallest – among educational workers (42,0%). Among COVID-19 convalescents, the level of humoral immunity reached 94,6%. Most of the seropositive volunteers (95,2%) did not have any symptoms of COVID-19, that is, they belonged to the category of asymptomatic carriers. Output. The results of a survey of a representative cohort of volunteers in the Kaliningrad region showed that they are characterized by a high level of population immunity, which makes it possible to expect a decrease in. © 2021 Interregional public organization Association of infectious disease specialists of Saint-Petersburg and Leningrad region (IPO AIDSSPbR). All rights reserved.
ABSTRACT
The first case of COVID-19 was diagnosed in St. Petersburg on March 2, 2020;the period of increase in the incidence lasted for 10 weeks, the maximum rates were recorded in mid-May, and subsequently there was a statistically significant decrease in the incidence. Objective: to determine the level and structure of community immunity to SARS-CoV-2 among the population of St. Petersburg during the period of intensive spread of COVID-19. Materials and methods. Selection of volunteers for the study was carried out through interviewing and randomization. The exclusion criterion was active COVID-19 infection at the time of the survey. 2713 people aged 1 to 70 years and above were examined for the presence of specific antibodies to SARS-CoV-2. Antibodies were detected by enzyme immunoassay. Results and discussion. Studies have shown that in St. Petersburg, in the active phase of COVID-19 epidemic, there was a moderate seroprevalence to SARS-CoV-2, which amounted to 26 %, against the background of a high frequency (84.5 %) of asymptomatic infection in seropositive individuals who did not have a history of COVID-19 disease, positive PCR result and ARI symptoms on the day of examination. The maximum indicators of herd immunity were established in children 1–6 years old (31.1 %), 7–13 years old (37.7 %) and people over 70 years old (30.4 %). Differences in the level of seroprevalence in the age groups of 18–49 years are statistically significant. The highest level of seroprevalence was found among the unemployed (29.7 %), healthcare workers (27.1 %), education sector (26.4 %) and business sector personnel (25 %). In convalescents, COVID-19 antibodies are produced in 75 % of cases. In individuals with positive result of PCR analysis carried out earlier, antibodies are detected in 70 % of the cases. The results of the study of herd immunity to SARS-CoV-2 are essential to forecast the development of the epidemiological situation, as well as to plan measures for specific and non-specific prevention of COVID-19. © 2020 Russian Research Anti-Plague Institute. All rights reserved.
ABSTRACT
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.