ABSTRACT
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.
ABSTRACT
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.
ABSTRACT
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.
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.