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.

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 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.