Features of the Formation of Seroprevalence to SARS-CoV2 in the Population of the Republic of Tatarstan during the Spread of COVID-19

Relevance. It is relevant to study the features of the formation and duration of the humoral immune response to a new coronavirus infection in a high-risk group of infection-among medical workers. Aims. To study the dynamics of the levels of specific antibodies (IgM and IgG) to SARS-CoV2 in unvaccinated MRs of the temporary infectious diseases hospital to assess the trends of the individual humoral immune response to a new coronavirus infection. Materials and methods. We monitored IgM and IgG to SARS-CoV-2 in 68 unvaccinated healthcare workers monthly from July 2020 to July 2021 by two-stage direct solid-phase ELISA using the test systems «SARS-CoV-2-IgG-ELISA-BEST» and «SARS-CoV-2-IgM-ELISA-BEST», Russia. Among them, there were 26.5% men and 73.5% women, the average age was 43.5 ± 1.51 years, doctors 52.9%, paramedical personnel 36.8% and junior staff 10.3%. 69.1% had a history of clinical manifestations of COVID19, among them 42.7% had a mild infection, 20.6% had a moderate infection, and 5.9% had a severe infection, 30.9% were asymptomatic. Statistical processing were carried out using the methods of variation statistics using the Excel statistical package and the WinPepi software product (version 11.65). Results. A decrease in the geometric mean value of IgM titers to SARS-CoV-2 (average monthly decrease of 6.40%) and an increase in the geometric mean value of IgG titers (average monthly increase of 4.26%). An individual assessment of the dynamics of antibodies from the day with the first positive result showed a decrease in the geometric mean values of antibody titers and IgM and IgG to SARS-CoV-2 (monthly average decrease of-23.56% and-1.18%, respectively). An individual assessment of the immune response made it possible to distinguish three groups according to the dynamics of IgM: M0-IgM in the blood were absent (50 ± 5.7446%);M1-IgM persisted for 1–2 months, followed by a rapid decrease in titer (16.176 ± 3.7943%);M2 – IgM remained in the blood for three or more months (33.824 ± 5.1033%). By the nature of the dynamics of IgG MR were divided into four troupes. With a downward trend in IgG titer: G0 – IgG does not exceed 95% of the upper confidence limit of the individual trend in any of the samples taken (19.118 ± 4.7686%), G1 – does not exceed 95% of the upper confidence limit of the individual trend starting from 3 months after the start observations (4.412 ± 2.4903%), G2 – there is an excess of 95% of the upper confidence limit of the individual trend starting from 3 months after the start of observation (69.118 ± 5.6027%);G3 – with a trend of increasing IgG titer (7.353 ± 3.1651%). Сonclusions. The results of serological monitoring as a whole indicate the formation of herd immunity in this cohort. Monitoring the intensity of the individual immune response to SARS-CoV-2 throughout the year reflects the natural course of the infectious process and is the basis for vaccination against COVID-19. The results of serological monitoring can be used to predict the epidemiological situation, plan specific and non-specific COVID-19, personalization of vaccination. © 2023, Numikom. All rights reserved.

Features of the population immunity to SARS-CoV-2 development in staff members of medical organizations during the spread of COVID-19

Background. The ongoing COVID-19 pandemic generates the urgent need of monitoring the herd immunity among healthcare workers as a high-risk group for infection. Aim. Determining the level and structure of population immunity to SARS-CoV-2 in the medical workers during the second peak of COVID-19 from August to November 2020. Material and methods. The study involved 15,158 medical workers from 91 medical organizations of the Republic of Tatarstan. The age of the examined stuff members varied from 18 to 74 years, the average age was 45.48±0.1016 years, most of them were women (13 627, 89.87±0.258%). Testing for the presence of total antibodies (immunoglobulin classes G, A and M) to SARS- CoV-2 was performed once by the enhanced chemiluminescence method. Statistical processing was carried out by methods of variation statistics and correlation analysis according to the Pearson method using MS Excel and WinPepi. Results. Seroprevalence to SARS-CoV-2 in medical workers was 35.23±0.388%. An increase in seropositive individuals level from 27.44±0.265% in August to 57.91±0.499% in November and an increase in the average geometric mean titer of total antibodies (immunoglobulin classes A, M, G) from 84.43 in August to 101.09 in November 2020 were detected. The level of individuals with antibodies increased with age from 18 to 59 years and decreased in group of 60-70 years. The largest proportion of seropositive to SARS-CoV-2 individuals was found among junior (42.01±1.384%) and middle grade (37.5±0.527%) medical staff of hospitals for patients with COVID-19, ambulance and emergency stations. Among the seropositive to the SARS-CoV-2 workers the proportion of asymptomatic forms of infection was 84.97±0.498%. According to the level of seroprevalence, municipal districts of the Republic of Tatarstan were divided into three groups: moderate - 8.9-39.0;average - 42.9-49.6, high level - 53.1-64.4. Сonclusion. An increase in seroprevalence to SARS-CoV-2 was revealed among medical workers of the Republic of Tatarstan from August to November 2020 during the second peak of COVID-19. © Eco-Vector, 2022. All rights reserved

Study of features of humoral immune response to the new coronavirus infection covid-19 among healthcare workers

Relevance. Since the beginning of the epidemic in China, there have been reports of nosocomial cases of SARS-CoV-2 infection, including among medical workers. Studies of the intensity of humoral immune response to the SARS-CoV-2 virus among medical workers who are much more likely to have professional contact with COVID-19 patients than are of particular importance. The aim is to study the seroprevalence and features of the humoral immune response to SARS-CoV-2 among medical workers. Materials and methods. The study included 61 medical workers from a multidisciplinary hospital in Kazan, which was redesigned to provide medical care to patients with new coronavirus infection, using the method of random sampling. The control group consisted of 60 non-medical workers. For the determination of IgG, a solid-phase ELISA was used. Statistical processing of the results was carried out using MS Excel software. The error of the relative value (M±m) was calculated, and the 95% confidence interval of the frequency of occurrence. To assess the significance of differences, the Student's test (t-test) was used for independent samples. Results. The proportion of those seropositive to SARS-CoV-2 in the study group was 45.9%, compared with 21.7% in the control group. Among medical workers seropositive to the SARS-CoV-2 virus, the proportion of asymptomatic forms was 18.5%, mild forms - 53.6%, moderate forms and severe forms 25%. Two forms of the formation of a humoral immune response among seropositive ones were revealed: the first is characterized by the gradual elimination of specific IgG antibodies to SARS-CoV-2 after 8 weeks from the onset of the first symptoms of COVID-19, the second form is an increase in specific IgG to SARS-CoV-2 and a higher value of the coefficient level of IgM positivity to SARS-CoV-2 after 8-10 weeks from the onset of the first symptoms. The group of seropositive, “raising antibodies”, prevailed over the group of individuals “eliminating antibodies”. Among seropositive medical workers, two forms of the formation of a humoral immune response were revealed: synchronous with the parallel elimination of IgG and IgM antibodies and a parallel increase in IgG and IgM. Conclusion. The study of the level of humoral immunity to COVID-19 in medical workers is important in terms of planning both anti-epidemic measures and predicting the effectiveness of the response to vaccination to SARS-CoV-2.

Study of the level and structure of population immunity to sars-cov2 in the population of the republic of tatarstan during the second peak of the spread of covid-19

Background. The COVID-19 pandemic has become a serious challenge for all of humanity due to the rapid global spread, high frequency of severe forms, increased mortality and required the development of new approaches to managing epidemiological processes. Serological studies are the most important tool for monitoring the infectious process, identifying risk groups, assessing the effect of vaccines used and epidemiological projections. Purpose. Conducting serological monitoring in relation to the modern transferred new coronavirus infection determining the level and structure of population immunity to SARS-CoV-2 in the population of the Republic of Tatarstan;maintaining the period of spread of COVID-19 from August to December 2020. Materials and methods. The study involved 41 444 residents of the Republic of Tatarstan, who filled out questionnaires that included clinical, anamnestic data and an epidemiological history in relation to COVID-19, who were tested for the presence of common antibodies (IgG, IgA and IgM) to the SARS coronavirus. CoV-2 by the method of enhanced chemiluminescence on the VITROS 3600 analyzer using the VITROS Anti-SARS-CoV-2 Total Reagent Pack test systems. Statistical processing was carried out by methods of variation statistics and correlation analysis according to the Pearson method using MS Excel and WinPepi. Results. Seropositivity to SARS-CoV-2 in the population of the Republic of Tatarstan averaged 35.8 ± 0.235%. An increase in the level of seropositive persons was noted from 29.95 ± 0.674% in August to 68 ± 9.33% in December. The highest proportion of seropositive individuals was found in was found in the group of the able-bodied population aged 18–59 years. The average geometric titer of antibodies was 4.2 (4.09–4.31), among seropositive – 89.29 (88.13–90.46). In the social and professional structure of the population, the largest proportion of seropositive individuals was found in was found among production workers 40.35 ± 2.177, creative professions – 40 ± 9.798;health care 35.24 ± 0.389;34.26 ± 1.218 unemployed and 33.06 ± 2.479 civil servants. Among the residents of the Republic of Tatarstan, seropositive to the SARS-CoV-2 virus, the proportion of asymptomatic forms of infection was 82.59 ± 0.446%. Сonclusions. There is a positive dynamics of seropositivity among the population of the Republic of Tatarstan. The results of sero-epidemiological monitoring can be used to predict the epidemiological situation, plan measures for specific and non-specific prophylaxis of COVID19. ©Sadykov MN et al.

STUDY OF FEATURES OF HUMORAL IMMUNE RESPONSE TO THE NEW CORONAVIRUS INFECTION COVID-19 AMONG HEALTHCARE WORKERS

Relevance. Since the beginning of the epidemic in China, there have been reports of nosocomial cases of SARS-CoV-2 infection, including among medical workers. Studies of the intensity of humoral immune response to the SARS-CoV-2 virus among medical workers who are much more likely to have professional contact with COVID-19 patients than are of particular importance. The aim is to study the seroprevalence and features of the humoral immune response to SARS-CoV-2 among medical workers. Materials and methods. The study included 61 medical workers from a multidisciplinary hospital in Kazan, which was redesigned to provide medical care to patients with new coronavirus infection, using the method of random sampling. The control group consisted of 60 non-medical workers. For the determination of IgG, a solid-phase ELISA was used. Statistical processing of the results was carried out using MS Excel software. The error of the relative value (M +/- m) was calculated, and the 95% confidence interval of the frequency of occurrence. To assess the significance of differences, the Student's test (t-test) was used for independent samples. Results. The proportion of those seropositive to SARS-CoV-2 in the study group was 45.9%, compared with 21.7% in the control group. Among medical workers seropositive to the SARS-CoV-2 virus, the proportion of asymptomatic forms was 18.5%, mild forms - 53.6%, moderate forms and severe forms 25%. Two forms of the formation of a humoral immune response among seropositive ones were revealed: the first is characterized by the gradual elimination of specific IgG antibodies to SARS-CoV-2 after 8 weeks from the onset of the first symptoms of COVID-19, the second form is an increase in specific IgG to SARS-CoV-2 and a higher value of the coefficient level of IgM positivity to SARS-CoV-2 after 8-10 weeks from the onset of the first symptoms. The group of seropositive, "raising antibodies", prevailed over the group of individuals "eliminating antibodies". Among seropositive medical workers, two forms of the formation of a humoral immune response were revealed: synchronous with the parallel elimination of IgG and IgM antibodies and a parallel increase in IgG and IgM. Conclusion. The study of the level of humoral immunity to COVID-19 in medical workers is important in terms of planning both anti-epidemic measures and predicting the effectiveness of the response to vaccination to SARS-CoV-2.

Experience in studying herd and individual immunity to the SARS-CoV-2 virus in medical workers

The aim was to study SARS-CoV-2 immunity among medical workers in Kazan. Materials and methods. Studied were serum samples from 348 medical workers from 10 medical organizations in Kazan, divided into groups according to the level of the alleged risk of infection of employees. To determine IgG, a two-stage direct version of the solid-phase ELISA and the test-system “SARS-CoV-2-IgG-ELISA-BEST” (Russia) were used. Results and discussion. At the time of the study and over the previous three months, the examined medical workers had no symptoms of acute respiratory viral infection or respiratory tract infections;there were negative results of examining nasopharyngeal/ oropharyngeal swabs for the presence of SARS-CoV-2 RNA. Seroprevalence for IgG to SARS-CoV-2 virus for different medical organizations in Kazan ranged within the scope of 3.3–30.8 % and averaged 16.4 %. The wide variation in seroprevalence values in medical workers of different medical organizations may indicate different levels of intensity of professional contacts and the effectiveness of anti-epidemic measures in these medical organizations. Among medical workers with seropositive results, the prevalence of persons with a very high coefficient of positivity (49.1 %) is observed, which characterizes high level of antiviral antibodies. The presence of a high proportion of seropositive individuals among medical workers, who have had an asymptomatic form of COVID-19 confirms the high intensity of the latent epidemic process, which must be taken into account when organizing preventive measures, including vaccination. © 2021 Russian Research Anti-Plague Institute. All rights reserved.

Seroprevalence study results to sars-cov-2 in healthcare workers: Age and professional aspects

Relevance. Age-related and occupational aspects of SARS-CoV-2 seroprevalence in healthcare workers are not well understood. Aims:Conduct a selective study of seroprevalence to the SARS-CoV-2 virus among 348 medical workers of 10 medical organizations in Kazan: seven multidisciplinary hospitals that have been re-profiled to provide medical care to patients with coronavirus infection, an ambulance station, a medical organization that carries out outpatient activities and a specialized clinic. Materials and methods. Among those surveyed on a professional basis, the groups «Doctors», «Nurses», «Junior medical personnel», «Other medical workers» were identified. The age structure of seroprevalence was studied in groups of 18–29, 30–39, 40–49, 50–59 and 60–69 years. For the determination of IgG, a solid-phase ELISA was used. Results. The proportion of medical workers (MR) of various medical organizations in Kazan seropositive for IgG to the SARS-CoV-2 virus is 16.4%. The wide variation in the seroprevalence value of MR groups of different medical organizations (3.3–30.8%) may indicate a different level of effectiveness of anti-epidemic measures in these institutions. The maximum rate was noted in the age groups – 18–29 years (21%) and 60-69 years (18.2%). According to the professional criterion, a comparable level of seroprevalence is shown for the categories «Doctors» and «Nurses» with a wide variation in indicators in professional groups, depending on a particular medical organization. The obtained results indicate the presence among medical workers who have suffered or have an asymptomatic course of infection caused by SARS-CoV-2, and confirm the relevance of further serological monitoring in medical organizations of various profiles. The results of serological monitoring, taking into account age and professional aspects, can serve as the basis for adjusting preventive measures on the basis of individual medical organizations, and taking into account the recommendations of Rospotrebnadzor and the selection of contingents for vaccination against SARS-CoV-2. Conclusions: For the MR of various medical institutions in Kazan, the seroprevalence for antibodies to the SARS-CoV-2 virus is 16.4%;Age aspects affect the level of seroprevalence in MR;The obtained results indicate the presence of persons among MR who have had or have an asymptomatic course of infection caused by SARS-CoV-2, and confirm the relevance of further serological monitoring in medical organizations of various profiles. © 2021, Numikom. All rights reserved.