COVID-19: the evolution of the pandemic in Russia. Report I: manifestations of the COVID-19 epidemic process

Background. The ongoing pandemic of a new coronavirus infection (COVID-19) determines the relevance of the analysis of epidemiological patterns of SARS-CoV-2 spread among the population of the Russian Federation. Aim — study of the manifestations of the epidemic process of COVID-19 in the Russian Federation in 2020–2022. Materials and methods. A retrospective epidemiological analysis of the incidence of COVID-19 in the Russian Federation was carried out from 03/30/2020 to 04/24/2022. The data from the Rospotrebnadzor report No. 970 “Information on cases of infectious diseases in persons with suspected new coronavirus infection”, information portal Stopcoronavirus.rf, etc. were used. The presence of SARS-CoV-2 RNA was confirmed by real-time RT-PCR. Results and discussion. The analysis of the manifestations of the epidemic process of COVID-19 in the Russian Federation in 2020–2022 showed the presence of two stages which differed depending on the influence of the biological factor and the ongoing anti-epidemic measures. There was a pronounced trend in the development of the epidemic process, starting from megacities (Moscow, Moscow region and St. Petersburg), which are major transport hubs and centers of migration activity of the population, to the regions of the Russian Federation. The SARS-CoV-2 pathogenicity has been shown to decrease with each subsequent cycle of the rise in the incidence of COVID-19 against the background of the increased contagiousness of the virus. Conclusion. As a result of the study, risk areas (megacities) and risk groups were identified. © 2022, Central Research Institute for Epidemiology. All rights reserved.

SEROPREVALENCE OF ANTIBODIES TO SARS-CoV-2 IN CHILDREN AGAINST THE BACKGROUND OF THE COVID-19 EPIDEMIC IN THE RUSSIAN FEDERATION

Objective: To study the seroprevalence of SARS-CoV-2 antibodies (AB) in children in the 2nd year of the COVID-19 pandemic in Russia. Materials and methods: Prospective cohort study. The seroprevalence research was conducted among 3670 children aged 1 to 17 y/o from 26 modelling regions of Russia (that have been participating earlier in the five stages of seromonitoring during 2020-2021). The serological testing was carried out in December, 2021. The work was carried out according to a unified methodology set by the Russian Federal Service for Supervision of Consumer Rights Protection and Human Well-Being with the Pasteur Institute of Epidemiology and Microbiology (Saint Petersburg, Russia). The plasma was obtained from 3 ml of venous blood, in which the level of AB to nucleocapsid (NC), and the SARS-CoV-2 receptor-binding domain (RBD) was determined by immunoferment method using reagents for qualitative and quantitative analysis. Results: The analysis of AB seroprevalence to NC and RBD showed the statistically significant increase in the share of seropositivity to RBD in children of all modelling regions (p<0.05). The most seropositive volunteers contained low levels of AB: 31.3-125.6 BAU/ml NC and 22.6-220 BAU/ml RBD. An increase in the level of AB to NC and RBD was accompanied by a decrease in the percentage of seropositive patients. Evaluating the contribution of children to the level of humoral immunity, convalescents (had been ill shortly before the examination), the «anamnesis» (had been ill at previous stages of seromonitoring) and asymptomatic (had been asymptomatically ill) groups were distinguished. The maximum contribution was made by children with asymptomatic cases of COVID-19 in anamnesis: In 82.3% (95% CI 81.1-83.6), of which 76.9% (95% CI 75.5-78.3) AB detected to RBD. The contribution of children of two other groups to the overall level of humoral immunity was 33 times less. Conclusion: Statistically significant predominance of AB to RBD above AB to NC and their main contribution to the level of humoral immunity to SARS-CоV-2 (p<0.001).

Factors associated with poor outcomes in pneumonia patients during the COVID-19 pandemics

Objective. Detection of additional factors favoring progression of COVID-19 and developing lethal outcomes in hospitalized patients. Materials and methods. Analysis of 98 medical records of lethal cases of patients that underwent hospitalization with diagnosis of COVID-19 associated pneumonia of two in-patient facilities of the Amur oblast and Khabarovsk krai was performed. Two groups were formed: first included medical records of patients hospitalized in severe condition (n = 52) and second group included patients with state of moderate severity (n = 46). Length of hospitalization stay, time from admission to the medical facility to progression of the disease, time from hospitalization to death and bacterial pathogens species composition isolated from lungs tissue autopsy material were analyzed. Statistical assessment of obtained data was performed with StatSoft Statistica 12.0. Results. Majority of patients of 1st and 2nd groups (66.7 ± 6.80% and 69.6 ± 6.78%) were hospitalized on fourth day of the COVID-19 clinical manifestations onset or later. Two thirds of patients hospitalized in severe condition progressed to critical health status on 1st–3rd day of hospitalization. Majority of second group patients (65.2 ± 7.02%) deteriorated from moderate severity to severe health condition on 4th–14th day of hospital stay. Bacteriological assessment analysis of autopsy material revealed that material obtained from first group showed more frequent absence of bacterial flora growth compared with second group both in the Amur oblast (44.4 ± 9.74% и 29.4 ± 11.39%) and in the Khabarovsk krai (в 40.0 ± 10.0% and 27.6 ± 8.45% of cases). Klebsiella pneumoniae (57.7 ± 5.86%) and Candida spp. (18.3 ± 4.59%) were revealed more frequently in the structure of diagnosed pathogens. Substantial proportion of pathogens (81.7 ± 4.59%) were isolated in autopsy material of patients which hospital stay was 4 days and longer. Prolonged hospital stay was associated with more frequent detection of K. pneumoniae and Candida spp. in patients that suffered from COVID-19 pneumonia and eventually died from the disease. With duration of hospitalization of 4 days and longer Acinetobacter baumannii – an extremely virulent pathogen with natural drug resistance was isolated from autopsy material. Conclusion. Factors influencing unfavorable outcomes of COVID-19 include signs of secondary bacterial infection as well as detection of aggressive drug-resistant bacterial microflora that most likely had nosocomial origin due to prolonged hospitalization. © 2021, Dynasty Publishing House. All rights reserved.

THE HERD IMMUNITY TO SARS-CoV-2 AMONG THE POPULATION OF THE NIZHNY NOVGOROD REGION AMID THE COVID-19 EPIDEMIC

The aim of the study was to assess the seroprevalence to the SARS-CoV-2 nucleocapsid in the population of the Nizhny Novgorod region against the background of COVID-19. Materials and methods. The work was carried out according to a unified methodology developed by Rospotrebnadzor with the participation of the St. Pasteur. The selection of volunteers for the study was carried out by the method of questioning and randomization. The exclusion criterion was active COVID-19 infection at the time of the survey. A total of 2829 volunteers were surveyed, divided into seven age groups. Venous blood samples were taken from all volunteers from EDTA vacutainers. In the blood plasma, the content of specific IgG to the SARS-CoV-2 nucleocapsid was determined by the enzyme immunoassay. Results. The population level of immunity to SARS-CoV-2 among the surveyed volunteers was 8,4% (95% CI 7,4–9,5). The largest proportion of seroprevalent persons was found among children aged 1–6 years — 15,9% (95% CI 8,2–26,7), the smallest in the group of volunteers aged 18–29 years — 6,0% (95% CI 3,8–8,9). During 3-stage serological monitoring, the proportion of seroprevalent volunteers increased to 22,5% (95% CI 20,3–24,9)%, or almost 2 times from the initial level (p<0,05). of the population of the Semenovsky district (22,7% (95% CI 10,9–41,8)), the smallest — in the city of Dzerzhinsk (2,4% (95% CI 0,5–7,1)%) Among convalescents after COVID-19, specific antibodies were detected in 47,2% (95% CI 30,5–69,6), which is 5,6 times higher than the average for the population. Among those who had verified contact with patients, specific IgG were detected in 17,6% (95% CI 12,9–23,5), which is 2,1 times higher than the average for the population. Among asymptomatic persons who had a positive PCR result, 53,3% (95% CI 30,5–86,6) were seropositive, which is 6,3 times higher than the average for the population. Of 225 seropositive people, 188 (88,4% (95% CI 76,6–101,6)) had the disease asymptomatic. Conclusion. The relatively low proportion of seroprevalent persons among the population may indicate a significant risk of further development of the epidemic process caused by COVID-19 in the territory of the Nizhny Novgorod region. © 2021,HIV Infection and Immunosuppressive Disorders. All Rights Reserved.

Characteristic of herd immunity among the population of Stavropol region amid the COVID-19 epidemic

Introduction. The first pandemic in the 21st century, caused by the pathogenic representative of the coronavirus SARS-CoV-2, began in the Chinese city of Wuhan, where the first outbreak of coronavirus pneumonia was recorded in December 2019. The disease spread so quickly around the world that already on February 11, 2020, WHO was forced to declare a pandemic of the “coronavirus disease 2019” COVID-19. The first case of COVID-19 in the Stavropol Territory was registered on March 20, 2020, and three weeks later, starting from the 15th week of the year, a steady increase in the incidence began, which lasted until the 52nd week. During the study period, the incidence increased from 21.1 to 28.3 per hundred thousand of the population. Growth 1.3 times. Purpose: to determine the dynamics of population immunity among the population of the Stavropol Territory in 2020-2021. during the period of an epidemic increase in the incidence of COVID-19. Materials and methods. The SARS-CoV-2 study was carried out according to a unified methodology within the framework of the program for assessing the population immunity of the population of the Russian Federation, developed by Rospotrebnadzor with the participation of the St. Pasteur. In total, 2688 people were examined, divided into 7 age groups. In the examined individuals, the level of specific IgG to the SARS-CoV-2 nucleocapsid was determined by the enzyme immunoassay. Results. The level of seroprevalence among residents of the Stavropol Territory was 9.8%. The largest proportion of seropositive individuals was found in the age groups 1-6 and 7-13 years old (19.2% and 19.7%, respectively). Seroprevalence had no gender differences and ranged from 9.3% to 10.8%. When assessing the distribution of the proportion of seropositive persons in different geographic territories of the region, it was found that the maximum proportion was found in the Kochubeevsky district (23.1%), the minimum in Kislovodsk (7.7%). Among convalescents, the content of specific antibodies to SARS-CoV-2 was noted in 73.3%, which is 7.8 times higher than the average population level. When conducting seromonitoring in the 2nd half of 2020, a 10-fold increase in seroprevalence was recorded, accompanied by a decrease in incidence from the 5th week of 2021. Among asymptomatic volunteers in whom SARS-CoV-2 RNA was detected by the polymerase chain reaction, antibody titers to viruses were found in 78.6%, which corresponds to the seroprevalence of convalescents. The proportion of seropositive persons among those who have come into contact with CO-VID-19 patients was 16.4%, (1.8 times higher than the average for the population). Out of 262 seroprevalent volunteers, the asymptomatic form of SARS-CoV-2 was detected in 92% of the examined, which indicates a significant role of the number of asymptomatic forms of infection in the epidemic process of COVID-19. Conclusion. The results of assessing the population immunity of the population of the Stavropol Territory indicate that it has not yet reached the threshold level at which a decrease in the intensity of the COVID-19 epidemic process can be expected. © 2021 Interregional public organization Association of infectious disease specialists of Saint-Petersburg and Leningrad region (IPO AIDSSPbR). All rights reserved.

Efficiency of Anti-Epidemic Measures that Ensure Access to Work in Rotational Shifts under Conditions of Covid-19 Pandemic

Objective – integral analysis of effectiveness of anti-epidemic measures applied towards employees of the Amur gas processing plant assigned for rotational work under conditions of COVID-19 pandemic. Materials and methods. Sero-epidemiological study included a questionnaire survey of 1461 workers who arrived through the “clean corridor” in the Amur Region, followed by sampling of biological material (blood and respiratory smears). Testing of blood sera for the presence of antibodies to SARS-CoV-2 of two classes (IgM and IgG) was carried out applying enzyme immunoassay. Using PCR, respiratory smears were examined for the presence of the agent RNA in them. Statistical processing of the results obtained was carried out using conventional methods. Results and discussion. The presence of antibodies of the IgG class was revealed in (4.7±0.55) % of cases. In a small cohort (1.7±0.34 %) of practically healthy individuals, asymptomatic infection was detected, confirmed either by a positive PCR result (0.76±0.23 %), or by the detection of IgM antibodies (1.0±0.08 %). On the basis of the study carried out by the Federal Service for Surveillance in the Sphere of Consumer Rights Protection and Human Welfare on August 01, 2020, “Temporary recommendations on the procedure for admitting to work on a rotational basis under the risk of COVID-19 spread in the Amur Region” were approved. These recommendations set out the algorithm for observation of incoming workers and the order for triage of shift workers after testing by ELISA and PCR. The results of the study demonstrate the effectiveness of anti-epidemic measures related to ensuring the procedure for admission to work on a rotational basis under the risks of the spread of COVID-19. © 2021 Russian Research Anti-Plague Institute. All rights reserved.

Herd immunity to sars-cov-2 in the population of the southern regions of the far east of Russia

The aim: to study the structure and dynamics of population immunity to SARSCoV-2 of the population of the Southern Regions of the Far East (SRFE): Khabarovsk, Primorsky Krai and Amur Region during the COVID-19 epidemic in 2020. Materials and methods. The work was carried out according to the program for assessing population immunity to SARS -CoV-2 of the population of the Russian Federation according to the methodology developed by the Rospotrebnadzor with the participation of the St. Petersburg Pasteur Institute. The study was approved by the ethical committee of the St. Petersburg Pasteur Institute. The selection of participants was carried out by a questionnaire method using cloud technologies. The volunteers were randomized by age by stratification into 7 age groups: 1–17, 18–29, 30–39, 40–49, 50–59, 60–69, 70+ years old. Territorial randomization consisted in limiting the engaging of volunteers – no more than 30 people from one enterprise. After the initialcross-sectionalstudy, a 3-stage seromonitoring was carried out, in which the same volunteers participated. Antibodies to the SARS-CoV-2 nucleocapsid were determined in peripheral blood serum by the enzyme immunoassay using an appropriate set of reagents produced by the State Scientific Center for Medical and Biological Sciences of the Rospotrebnadzor (Obolensk). Statistical analysis was performed using the Excel package. The confidence interval for the proportion was calculated using the A. Wald, J. Wolfowitz method with A. Agresti, B.A. Coull’s correction. The statistical significance of the differences was calculated online using a specialized calculator. The statistical significance of the differences was assessed with a probability of p < 0.05, unless otherwise indicated. Results. In a comparative analysis, the highest morbidity was observed in the Khabarovsk Territory, the lowest – in the Primorsky Territory. The level of seroprevalence among the population of the region was 19.6 % (95 % CI: 18.2–21.1) in the Khabarovsk Territory, 19.6 % (95 % CI: 18.1–21.2) in the Primorsky Territory19,6 % and 45,5 % (95 % CI: 43.7–47.3) in the Amur region. The highest seroprevalence was noted among 1–17 years old children, mainly due to the subgroup of 14–17-years-olds. The smallest proportion of seropositive was found among 40–49-year-olds in the Khabarovsk Territory (14.7 %, 95 % CI: 11.2–18.6), 18–28-year-olds in the Primorsky Territory (13.3 %, 95 % CI: 10.0–17.1) and 30–39-year-olds in the Amur Region (36.3 %, 95% CI: 31.7–41.6). No statistically significant dependence of seroprevalence on territorial and occupational factors has been established, with the exception of an increase in the proportion of seropositive medical workers in Primorsky Territory. In the process of 3-stage seromonitoring, a regular increase in the proportion of seropositive people was revealed in all SRFE. The resulting tendency is correctly describedby a second-order polynomial. Arelationship was revealed between the number of convalescents and persons in contact with them, which made it possible to calculate the base reproductive number (R0) in the range from 1.4 (Primorsky Territory) to 2.4 (Amur Region). Analysis of seroprevalent volunteers showed that the number of asymptomatic individuals varied from 94.1 % (95 % CI: 92.8–95.3) to 98.3 % (95 % CI: 98.8–99.2). This indicates that most of the volunteers had COVID-19 asymptomatically. Conclusions. A comparative study showed the prevalence of seroprevalence in the Amur Region compared with the Khabarovsk and Primorsky Territories. The relationship between the number of convalescents and persons in contact with them was noted. The value of the base R0 is calculated. It has been shown that more than 90 % of seropositive individuals in the COVID-10 SRFE were asymptomatic. © 2021 Scientific Centre for Family Health and Human Reproduction Problems. All rights reserved.

[Herd immunity to SARS-CoV-2 in the Novosibirsk Region population amid the COVID-19 pandemic].

AIM: To determine the level of SARS-CoV-2 seroprevalence among the Novosibirsk Region population against the background of the COVID-19 pandemic. MATERIAL AND METHODS: The work was carried out in 2 phases: 1) a cross-sectional cohort study performed 28.06- 15.07.2020; 2) longitudinal cohort 3-stage seromonitoring: 1st stage 28.06-15.07.2020; 2nd 14.09-04.10.2020; 3rd 10-30.12.2020 The work was carried out according to a unified methodology developed by Rospotrebnadzor with the participation of St-Petersburg Pasteur Institute, taking into account the recommendations of the WHO. IgG antibodies to the SARS-CoV-2 nucleocapsid protein were detected by ELISA using a kit of reagents produced by the SRCMSB (Obolensk) according to the manufacturer's instructions. Statistical analysis was performed using Microsoft Excel 2010 and other programs. RESULTS: The seroprevalence in the region's population was 9.1% (95% CI 8.0-10.2): maximum in children 14-17 years old (17.6%, 95% CI 12.3-23.9) and persons over 75 years (14.8%, 95% CI 11.4-18.8), minimum among persons 30-39 years old (4.9%, 95% CI 3.0-8.0). Increased rate was noted among the unemployed (15.4%, 95% CI 9.9-17.1) and other individuals (13.0%, 95% CI 8.6-18.5). Seroprevalence was 33.3% (95% CI 16.3-59.0) in COVID-19 convalescents and 19.0% (95% CI 13.9-25.0) in contact persons. More than 94.7% (95% CI 91.2-97.2) of seropositive individuals were asymptomatic. During the serological monitoring, seroprevalence increased from 7.4% (95% CI 6.2-8.9) at 1st stage 1 to 12.4% (95% CI 10.6-14.3) at 2nd , and 31% (95% CI 28.8-33.3) at 3rd stage. CONCLUSION: SARS-CoV-2 herd immunity has not reached the threshold level, this does not exclude exacerbation of the epidemic process.

Structure of herd immunity to SARS-COV-2 in the Krasnoyarsk region population in the COVID-19 epidemic

Purpose. Determination of the SARS-CoV-2 population humoral immunity among the population of the Krasnoyarsk Territory during the COVID-19 epidemic. Materials andmethods. The study was carriedoutas a partof projectfor assessing population immunity to SARS-CoV-2 among the population of Russian Federation using unified methodology developed by Rospotrebnadzor, with the participation of the Research Institute for Epidemiology and Microbiology named by Pasteur, and taking into account the recommendations of the WHO. The work involved 2907 volunteers, selected by the online survey and randomization by age and territory. All volunteers were divided into 7 age groups: 1–17, 18–29, 30–39, 40–49, 50–59, 60–69, 70 and older (70+), including a total 246–449 people. Population immunity testing was carried out during the formation of groups (1st stage), and then twice more, with the interval of 6–8 weeks. Serum was obtained from venous blood samples obtained from volunteers, in which antibodies to the SARS-CoV-2 nucleocapsid were determined by the enzyme immunoassay. The results were analyzed by methods of nonparametric statistics: median, interquartile range, rank correlation coefficient were calculated in the Excel statistical package. The confidence interval to seroprevalence indicators (95% CI) was calculated using the WinPepi statistical package (version 11.65). The statistical significance of the differences was assessed with a probability level of p ≤ 0.05. Results. The seroprevalence of the population of the Krasnoyarsk Territory during the 5-month period of seromonitoring had increased 3.3 times from 12.8% (95% CI 11.3–14.4) to 41.7% (95% CI 39.4–4.0), while the grouping by age had not revealedany peculiarities throughoutthe study. The trendtowards a decrease in the incidence was formedon the 6thweekof2021. The seroprevalence ofconvalescents after COVID-19 during the initial testing was 61.5% (95% CI 40,6–79.8), among those who were in contact with patients with COVID-19 or convalescents – 23.8% (95% CI 13.9–36.2) . Among the volunteers, 347 seropositive persons were identified, 324 of which were observed asymptomatic course. Conclusion. The structure of the population humoral immunity to SARS-CoV-2 of he population of the Krasnoyarsk Territory has been investigated. It was found that an increase in seroprevalence to 41.7% (95% CI 39.4–4.0) was accompanied by a decrease in morbidity. © 2021 Scientific Centre for Family Health and Human Reproduction Problems.

Peculiarities of seroprovalence to SARS-CoV-2 in the population of the middle and southern urals in the early period of the COVID-19 pandemic

Relevance. At the end of 2019, the world was confronted with a novel coronavirus (SARS-CoV-2), In January 2020, WHO declared an epidemic related to SARS-CoV-2, a health emergency of international importance, and in March characterized the spread of the world. diseases like a pandemic. Purpose of the study. Conduct a comparative analysis of the seroprevalence of the population of the Sverdlovsk and Chelyabinsk regions – the largest administrative territorial entities of the Middle and Southern Urals – against the backdrop of the COVID-19 pandemic. Materials and methods. The work was carried out under the program of the first stage of assessing the seroprevalence of the population of the Russian Federation according to a unified methodology developed by Rospotrebnadzor of the Russian Federation with the participation of the Saint Petersburg Pasteur Institute. The selection of participants was carried out by the method of questioning and randomization. The presence of antibodies to the SARS-CoV-2 nucleocapsid was determined in blood serum by the enzyme immunoassay. Results. Comparative analysis of the results showed that the incidence rate of COVID-19 in the Chelyabinsk region was consistently lower, and the seroprevalence at the first stage of the study was statistically significantly higher (p <0/05) than in the Sverdlovsk region. It was found that the incidence in both regions had a direct correlation with population density (r = 0.59;p <0.05). There were no differences between the compared areas in terms of seroprevalence among convalescents, people who had contact with COVID-19 patients, and asymptomatic volunteers with a positive PCR test. When analyzing seroprevalent volunteers in both regions, it was shown that the number of asymptomatic individuals varied within 94.4 ± 1.2% – 95.0 ± 0.95%. These data indicate that the majority of volunteers tolerated COVID-19 asymptomatically. Conclusions. A comparative study showed a statistically significant predominance of seroprevalence among the population of the Chelyabinsk region. It was found that an increase in seroprevalence at the population level was accompanied by a decrease in morbidity. Shown is a direct relationship between population density and the incidence rate. More than 90% of seropositive individuals in the compared areas showed asymptomatic course of coronavirus infection. © 2021, Numikom. All rights reserved.

Humoral Immunity to Sars-CoV-2 Among The Population of Murmansk Region Amid COVID-19 Epidemic

Purpose of the study. Determination of the level and structure of population immunity to SARS-CoV-2 among the population of the Murmansk region against the background of the incidence of COVID-19. Materials and methods. The study was carried out according to a unified method for determining the seroprevalence of the population, developed by Rospotrebnadzor with the participation of the St. Petersburg Pasteur Institute. A total of 3117 volunteers were examined, distributed into 7 age groups. The content of antibodies to SARS-CoV-2 was determined by ELISA using a set of reagents for analyzing human serum or plasma for the presence of specific immunoglobulins of class G to the nucleocapsid of the SARS-CoV-2 virus produced by the FBUN GNCPMiB Rospotrebnadzor (Obolensk) in accordance with the instructions for application. Results. The level of population immunity in the Murmansk region as a whole was 31,2%. The highest seroprevalence was found among children aged 1–6 and 7–13 years (35.6% and 44,1%, respectively), the lowest among the elderly population aged 60–69, as well as 70 and more years (20,4% and 20,9%, respectively). In the cities of the Murmansk region. the herd level of immunity varied from 19,6% (Kola city) to 46,1% (Kandalaksha city). It was not possible to find a reliable relationship between the incidence of the population of the cities of the Murmansk region and seroprevalence. The highest level of seroprevalence was noted among office workers (38,0%), the lowest among transport workers (19,5%). In the presence of contacts with patients with COVID-19, seropositivity increased 1,4 times compared to the average population value. The level of specific humoral immunity in convalescents after COVID-19 is 64,1%, which is 2,2 times higher than the average for half-day. The proportion of asymptomatic forms among seroprevalence volunteers was 89%. © 2021. All Rights Reserved.

FEATURES OF DEVELOPING SARS-CoV-2 NUCLEOCAPSID PROTEIN POPULATION-BASED SEROPREVALENCE DURING THE FIRST WAVE OF THE COVID-19 EPIDEMIC IN THE RUSSIAN FEDERATION

The novel coronavirus (SARS-CoV-2) pandemic, dubbed COVID-19, has become one of the most serious challenges for human populations in the vast majority of countries worldwide. Rapid spreading and increased mortality related to it required new approaches to manage epidemic processes on a global scale. One of such approaches was based on analyzing SARS-CoV-2 seroprevalence associated with COVID-19. Our aim was to summarize the results on assessing seroprevalence to the SARS-CoV-2 nucleocapsid antigen (Nc) in residents from 26 regions of the Russian Federation, carried out during the first wave of the COVID-19 epidemic. Materials and methods. Seroprevalence distribution was examined in 26 model regions of the Russian Federation according to the unified method developed by the Rospotrebnadzor with the participation of the Federal State Institution Saint Petersburg Pasteur Research Institute of Epidemiology and Microbiology. Such approach implied formation of a group of volunteer subjects in model geographic region who were tested by ELISA for anti-Nc serum antibody level in peripheral blood. Analyzed primary data obtained in separate regions were either accepted for publication or released. Results. The current paper finalizes the data obtained in all 26 regions of the Russian Federation. The total SARS-CoV-2 seroprevalence was 19.5 (10.0-25.6)% with the maximum and minimum value found in the Kaliningrad Region and the Republic of Crimea, respectively (50.2% vs. 4.3%). A pattern of age-related seroprevalence distribution indicates insignificant predominance of seroprevalence among subjects of 1-17 years old: 22.1 (13.1-31.8)%. Among COVID-19 convalescents positive for SARS-CoV Nc antibodies it reached 60.0 (40.0-73.3)%. The number of contact persons comprised 6285 subjects or 8.5% of total volunteer cohort, with the level of seroprevalence reaching up to 25.3 (17.95-35.8)%. A direct correlation was revealed between levels of seroprevalence in convalescent and contact volunteers. In addition, the reproductive number for SARS-CoV was calculated comprising 5.8 (4.3-8.5) suggesting that one convalescent subject can infect at least 4 healthy individuals. A high level of asymptomatic forms of COVID-19 among seropositive subjects was confirmed empirically comprising up to 93.6 (87.1-94.9)%. Conclusion. A single cross-sectional study performed during 2020 June-August timeframe allowed to assess pattern of sex- and age-related COVID-19 seroprevalence for general population in 26 Russian Federation regions. The data obtained may serve as a basis for the longitudinal cohort investigation with serial subject sampling. The timing and duration of study will be determined by dynamics of ongoing COVID-19 epidemic.

Assessment of population immunity to SARS-CoV-2 virus in the Rostov Region

By August 2020, more than 850000 cases of new coronavirus infection (COVID-19) caused by SARS-CoV-2 were confirmed in the Russian Federation, with the Rostov Region as one of the ten most affected regions in Russia. The spread of the disease is largely determined by the state of population immunity in a certain area. Our research focuses on specific humoral immune response and estimates the level of herd immunity to SARS-CoV-2 virus among the population of the Rostov Region. Materials and methods. The study involved 3,048 people;the volunteers participating in the study were divided into seven age groups. The content of antibodies to SARS-CoV-2 was determined applying ELISA using a kit for the analysis of human serum or blood plasma for the presence of specific IgG to the nucleocapsid of the SARS-CoV-2 virus, manufactured by the State Scientific Center of Applied Microbiology and Biotechnology (Obolensk) in accordance with the instructions for use. Results and discussion. The assessment of seroprevalence to SARS-CoV-2 in the Rostov Region showed that the proportion of people positive for IgG to the new coronavirus was 16.5 %, the range of seropositive individuals in the general population was between 13.9 % and 19.1 % (p<0.05). There were no significant gender differences in the degree of seroprevalence with a positive result registered in 16.6 % of women and 16.5 % of men. A high level of humoral immunity to SARS-CoV-2 was established in individuals aged 1–17 against the background of low incidence rates, which may indicate the dominance of asymptomatic forms of the disease in this age group. The highest level of seropositivity was found in preschool children (33.6 %), students (29.3 %), employees (17.3 %), and education professionals (15.3 %). © 2020 Russian Research Anti-Plague Institute. All rights reserved.

Characteristics of the herd immunity to SARS-CoV-2 in residents of the saratov region under COVID-19 epidemic

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.

Features of etiology of community-acquired pneumonia associated with COVID-19

Objective: comparative study of the etiological structure of community-acquired pneumonia in SARSCoV-2 “+”and SARS-CoV-2 “-“patients who sought help from medical organizations in the Rostov Region. Materials and methods. Biological material from 508 patients diagnosed with community-acquired pneumonia who were on outpatient treatment or in hospitals in Rostov-on-Don was studied. Verification of respiratory viruses, including SARS-CoV-2 RNA, as well as M. pneumoniae, C. pneumoniae, and L. pneumophila was performed by polymerase chain reaction in nasopharyngeal smears. Bacteriological analysis of sputum was carried out using differential diagnostic media, identification of isolated pathogens was carried out using time-of-flight mass spectrometry on Autoflex (Bruker Daltonics) with BioTyper 3.0 software. Results and discussion. During the spread of a new coronavirus infection in the Rostov Region, the main etiological agent of community-acquired pneumonia is the new SARS-CoV-2 coronavirus. Specific character of pneumonia in patients with laboratory-confirmed COVID-19 is a higher incidence of mixed infection of both viral and bacterial etiology. Against the background of detection of a new coronavirus infection in patients with pneumonia, cases of detection of other types of coronaviruses have been registered (HKU-1,OC43, HL-63 and 229е). The most common etiological agent of bacterial pneumonia in patients was Streptococcus spp., both in patients with COVID-19-associated pneumonia and in patients who tested negative for SARS-CoV-2. Coronavirus patients represent a high risk group for the development of mycotic lung lesions. © 2020 Russian Research Anti-Plague Institute. All rights reserved.

Mobile complexes of the specialized anti-epidemic teams (SAET) of the rospotrebnadzor as an effective tool in the implementation of measures to counter new coronavirus infection COVID-19

The mobile complexes of the specialized anti-epidemic teams (SAET) of the Rospotrebnadzor (mounted on the platform of auto chassis) have been actively involved in implementation of operational measures to counter COVID-19 in the Russian Federation, aimed at management and conducting of diagnostic studies. Analysis of the activities of mobile SAET in Moscow and Makhachkala made it possible to formulate the basic principles of organizing their work in the most difficult period of negative development of the situation, increasing incidence and insufficient readiness of laboratory bases for mass research: tactics of advance actions, flexibility in using the potential of SAET mobile complexes, monitoring over the implementation of anti-contamination measures at all stages of PCR analysis and the development of a consultative and methodological (training) aspects of activities of the team specialists. The use of mobile SAETs of the Rospotrebnadzor once again demonstrated their significance as a universal tool to counter epidemics of infectious diseases. © 2020 Russian Research Anti-Plague Institute. All rights reserved.

Distribution of SARS-CoV-2 seroprevalence among residents of the Republic of Tatarstan during the COVID-19 epidemic period

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.

Herd immunity of sars-CoV-2 among the population of Kalinigrad region amid the COVID-19 epidemic

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.