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 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.

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.

Herd immunity to SARS-CoV-2 among the population in Saint-Petersburg during the COVID-19 epidemic

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.

Assessment of the herd immunity to SARS-CoV-2 among the population of the leningrad region during the COVID-19 epidemic

The first case of COVID-19 was registered in the Leningrad Region on March 13, 2020. The period of increasing intensity of the epidemic process lasted 8 weeks. One month after reaching the maximum incidence rate, a study was organized to determine seroprevalence to COVID-19 among the population of the Region. Objective of the study was to determine the level and structure of community immunity to SARS-CoV-2 virus in the population of the Leningrad Region in the period of intensive COVID-19 transmission. Materials and methods. The work was carried out within the framework of the Rospotrebnadzor project on assessment of community immunity to the SARS-CoV-2 virus in the population of the Russian Federation. 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 study has showed that the herd immunity of the population of the Leningrad Region was 20.7 %. The maximum level has been established in children 1–6 years old (42.3 %) and people over 70 years old (29.0 %). The highest level of seropositivity, except for children and older people, was found among the unemployed (25.1 %). The lowest level of seroprevalence was detected in civil servants (12.8 %) and military personnel (16.7 %). It has been shown that the risk of infection increases by 1.5 times in case of contacts with COVID-19 patients. After exposure to COVID-19 virus, antibodies are produced in 82.1 % of the cases. In individuals with a positive PCR test result obtained earlier, antibodies are detected in 82.8 % of cases. The share of asymptomatic forms among seropositive residents of the Leningrad Region was 86.9 %. The results of assessing the herd immunity to SARS-CoV-2 in the population of the Leningrad Region indicate that during the period of intensive COVID-19 transmission, an average level of seroprevalence was formed. A significant proportion of asymptomatic forms of infection characterizes the high intensity of the latently developing epidemic process. The results obtained should be taken into account when organizing preventive measures, including vaccination, and predicting morbidity rates. © 2020 Russian Research Anti-Plague Institute. 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.