Relevance. It is known that the main trigger for the development of the pandemic was the genomic diversity of viruses. Meanwhile, we did not find any studies on the influence of population susceptibility on the complex process of evolutionary transformations of the SARS-CoV-2 virus and their interdependent variability during the development of the pandemic. Aim. The study of the interdependent variability of two heterogeneous populations interacting in the dynamics of the development of the COVID-19 pandemic - the virus population and the population. Materials and methods. The study was conducted in the city of Perm from 03/01/2021. (Beginning of sequencing of the SARS-CoV-2 virus in the territory) until 01.01.2023. In weekly dynamics, the following were studied: SARS-CoV-2 genomic diversity (molecular genetic study of 2521 samples of biomaterial from patients), seroprevalence of the population (366,804 blood sera were examined for the presence of IgG), morbidity, disease prevalence rate and mortality (according to official statistics). The interpretation of the results was carried out in accordance with the provisions of the theory of self-regulation of parasitic systems by V.D. Belyakov. Results and discussion. An analysis of the genomic diversity of the virus during the pandemic made it possible to distinguish 5 periods. Three periods were characterized by the homogeneity of the pathogen population, when the variants Alpha, Delta and Omicron circulated. Two periods were characterized by the simultaneous circulation of two variants of viruses due to the adaptation of the virus to the changed habitat. Thus, the circulation of the Alpha variant in a population heterogeneous in terms of susceptibility (the proportion of seropositive ones increased to 52%) caused mutational changes in the virus genome with the formation of high transmission properties and high pathogenicity (according to the theory of V.D. Belyakov, the phase of formation of an epidemic variant). The formation of the epidemic variant of the pathogen (Delta genovariant) occurred within 12 weeks, it dominated for more than 6 months, increasing the incidence by 2.8 times, mortality by 17.3 times (epidemic spread phase). The increase in the incidence and large-scale vaccination increased the seroprevalence of the population to 70% or more. The Delta variant begins to adapt to a new habitat with a high proportion of immune organisms, the formation of the Omicron genovariant with high transmission and evasion of the immune response is underway (the phase of formation of the pathogen reservation variant). The pathogen population is heterogeneous; Delta and Omicron circulate simultaneously. Morbidity increases by 2.9 times, RT by 1.3 times, and mortality decreases by 5.1 times. Omicron replaces the Delta genovariant within 5 weeks, mortality decreases, while maintaining the distribution coefficient (reservation phase). Conclusions. Interdependent variability of the virus and the susceptibility of the population determined the phase development of the pandemic.

Relevance. COVID-19 is accompanied by high production of cytokines - immune molecules, imbalanced regulation of which leads to disruption of the immune response. Therefore, the study of cytokine status in both vaccinated and re-vaccinated patients is necessary to develop an immunoprophylaxis strategy for COVID-19. Aim. To evaluate the cytokine status in COVID-19 survivors and vaccinated employees of a health care facility against this disease. Materials and Methods. Production levels of cytokines (IL-4, IL-10, IFN-γ and TNF-α) were determined by quantitative enzyme immunoassay in serum of 144 volunteers. Results and discussion. A significant 1.5-fold increase in IL-10 and 2.0-fold increase in TNF-α was found in the group of re-invaccinated overinfected volunteers, and a 2.0-fold decrease in IL-4 compared with the vaccinated group. An inverse correlation between IL-4 and IFN-γ levels and timing after the disease was detected. A significant decrease in IL-4 in survivors (Omicron variant) and an increase in IL-10 in the survivors at the beginning of the pandemic as compared to other re-vaccinees was established. In the vaccinated group, regardless of the vaccine used, IL-10 and TNF-α decreased significantly after revaccination. No statistically significant differences were found between the cytokine status parameters in the survivors before and after vaccination. The predominance of the cellular component of immunity was established in all the examined groups, and the highest proportion of persons with a humoral immune response was detected among the vaccinated volunteers, while the highest proportion of persons with a mixed immune response was detected among the overexperienced non-vaccinated patients. Conclusions. The results obtained supplement the available data on coronavirus infection and indicate the need for further research.

Relevance. To maximize the success of COVID-19 vaccination, it is necessary to consider the sensitivity of population health not only to these specific exposures, but also to the inherent socioeconomic factors that can modulate the effectiveness of health interventions. Aims. To assess the relationships between infection, mortality and the fatality ratio from COVID-19 in the countries of the world with the proportion of vaccinated in the population, as well as the relationship of the epidemic situation on COVID-19 with the parameters of the well-being of the population based on a cross-sectional study. Materials and methods. Statistical analysis used the data of the portal Our World in Data as of 15/12/2021, as well as UNO data on human development. Results. The frequencies of infection and death were higher the higher the human development index of countries. The inverse correlation of vaccination rates with infection and mortality rates was typical only for countries with very high human development. In the same group of countries, the infection fatality rate was the lowest. Conclusion. The nature of the correlations between the level of vaccination and the parameters of the epidemic situation is not the same for countries with different levels of human development. Apparently, a number of socio-economic factors, including the integral level development of the country and the level of urbanization, can influence the effectiveness of vaccination.

Relevance. Violation of the regulations on the use of personal protective equipment (PPE) by medical workers when providing medical care to patients with COVID-19 (COVID-19) at their workplaces and in other situations requiring PPE is fraught with serious consequences for the health and life of medical personnel and patients. Aims. To assess the impact of violations in the use of PPE on the incidence of COVID-19 of personnel of medical organizations of various profiles, including when providing medical care to patients with COVID-19. Materials and methods. The study used the method of cross-sectional retrospective simultaneous online questionnaire to assess the effectiveness of preventive measures against the spread of COVID-19, conducted from January to March 2022. The results of an anonymous online survey of various categories of personnel of medical, scientific and educational medical organizations of the Russian Federation providing medical care to patients with COVID-19 (n = 6032 people) were analyzed. Results. The study showed the greatest epidemiological significance in the formation of the risk of SARS-COV-2 infection by the irregular use of masks and gloves in the workplace (when providing medical care). The results of the assessment of the strength of the connection of violations in the use of personal protective equipment with infection with SARS-CoV-2 of the studied groups of personnel are presented. It is shown that the irregular wearing of face masks in the workplace when providing medical care has the most pronounced association with the risk of infection of all the factors studied. It is noted that statistically significantly more often the irregular use of masks and gloves in the workplace was allowed by students and nursing staff. Conclusions. The importance of compliance with the regulations for the use of personal protective equipment by medical workers is shown, not only when providing medical care to patients with COVID-19, but also at home, as well as the impact on the incidence of COVID-19 of the irregularity of the use of PPE by medical personnel in various conditions, including when providing medical care to patients with COVID-19.

Relevance. The demographic situation in the Russian Federation over the past decades has been characterized by negative dynamics, while the two key indicators, the ratio of which affects this, are birth and death rates. Of particular interest in this case are malignant neoplasms (MNs) of the organs of the reproductive system, which can both affect the decline in fertility, especially when it comes to the age group under 40, and make a significant contribution to the structure of the population mortality. Аim. Analyze the changes in mortality rates from cancer of the reproductive organs among the population aged 15 to 39 years, their dynamics and structure in the Russian Federation for 2011–2020. Materials and methods. To calculate the indicators, an analysis was carried out of the data of the forms of the federal state static observation on the distribution of the deceased by sex, age groups and causes of death by Rosstat (FSN-C51) and statistical information on the age and sex composition of the population of the territories of the Russian Federation. Results. The highest «crude» mortality rates were noted in the Siberian and Far Eastern Federal Districts (5.04 (95% CI = 4.49–5.58) and 5.00 (95% CI = 4.09–5.90) per 100 thousand of the population, respectively), the smallest – n the regions of the North Caucasus Federal District (2.58 (95% CI = 2.06 - 3.11) per 100 thousand of the population). Significant gender differences were also identified. Female mortality from malignancies of the reproductive organs was significantly higher (the "crude” mortality rate among women was found to be 7.57 (95% CI = 7.22–7.92) versus 0.72 (95% CI = 0.61–0.82) among men per 100 thousand) due to the dominance of oncological lesions of the cervix and mammary gland at an earlier age. Conclusion. The identified features of the manifestations of mortality from cancer of the reproductive organs for various territories and population groups can serve as a rationale for strengthening the existing preventive measures, such as vaccination against HPV, as well as for developing new strategies aimed at improving the demographic situation.

Relevance. In connection with the advent of new diagnostic immunological tests, it became possible to determine a potential focus of infection not only through the identification of patients with tuberculosis, but also through the identification of patients infected with M. tuberculosis, who still do not have manifestations of a local form of the disease. This made it possible to search for persons who were infected with an unknown source of tuberculosis infection in order to conduct an in-depth epidemiological investigation and detect hitherto unknown foci of tuberculosis. Aims. To study the effectiveness of identifying the source of infection in the environment of a patient with a positive immunological test for tuberculosis («indicator» patient). Materials and methods. 1) A retrospective study of the data of all 30 patients with tuberculosis in the period from 2014 to 2019 in Moscow, identified by indicator patients with a positive immunological test, was carried out. 2) A cohort of patients with latent tuberculosis infection with and without HIV infection (Moscow) was studied in the period 2020–2021. to determine the prevalence of latent infection in the close circle of communication of indicator patients. Results. Patients with tuberculosis, forming hidden foci and identified by the indicator patients infected by them with a latent infection, in 56.7% of cases were not examined for tuberculosis for 2–10 years, in 50.0% they suffer from tuberculosis with registered bacterial excretion, in 46.7% of cases are internal or external migrants. The prevalence of latent tuberculosis infection among indicator patients is 10%, which is many times higher than the prevalence of latent tuberculosis infection among the permanent population of Moscow (less than 1%), in HIV-infected risk groups (up to 5%), in known foci of tuberculosis on average in Moscow (5%). The TB notification rate in the environment of indicator patients with latent tuberculosis infection is 38.8 per 100,000 of the corresponding group and exceeds that among the permanent population of Moscow by 5.4 times. Conclusion. A modified epidemiological investigation aimed at examining the environment of persons with latent TB infection among adults makes it possible to identify TB patients who have infected indicator patients and to identify other infected patients.

Relevance. In recent years, there has been an increase in the incidence of a number of vaccine-preventable diseases. The health of military personnel directly affects the combat effectiveness of the army. Aim. Preserving the health of the military and ensuring the sanitary and epidemiological well-being of the troops is one of the most important tasks. Result. Approaches to vaccination of persons subject to conscription for military service and a list of infections against which they should be vaccinated (influenza, meningococcal and pneumococcal infections, chickenpox, COVID-19) are presented. Vaccines, schedule and features of vaccine administration are described. A list of the main regulatory documents for vaccination is provided. Conclusion. Vaccine prevention of persons subject to conscription for military service is an important strategic task, the implementation of which depends on coordinated work between military and civilian healthcare. Vaccination coverage of persons subject to conscription for military service must reach 100%.

Relevance. Diphtheria is one of the dangerous diseases that threaten human life. Immunization is the only means of creating a favorable epidemiological situation. Ensuring the immunity of the population to this infection prevents the occurrence of the rise and spread of diphtheria among the population. One of the ways to assess the state of specific immunity to diphtheria is annual serological monitoring. Aims. Assessment of the state of antidiphtheria immunity in different age groups of the population of the Russian Federation based on seromonitoring data for 2015–2021. Materials and methods. The data of serological monitoring of diphtheria and the state of vaccination of the population by indicator groups from 85 subjects of the Russian Federation in 2015–2021 were analyzed. In just 7 years, in terms of seromonitoring in Russia, 439,874 people were examined for the presence of antibodies to diphtheria, including 73,559 children in the age group of 3–4 years, 74,424 adolescents aged 15–17 years, and 291,891 adults aged 18 and older. During the same period, 12,154 controlled blood sera from 20 subjects of the Russian Federation were examined. In the age group of 3–4 years – 1834 children, 15–17 years – 1366 teenagers, 18–29 years – 1711 adults, 30–39 years – 1724 adults, 40–49 years – 1918 adults, 50–59 years – 1798 adults, 60 years and older – 1803 adults. The presence of antibodies to diphtheria was determined in the course of passive hemagglutination. The protective titers of antibodies were taken to be dilution of sera with a titer of 1:20 or more, the intensity of anti-diphtheria immunity was assessed as follows: antibody titers in dilution of sera 1:20–1:40 – low titers, 1:80–1:160 – medium and 1:320 or more – high titers of antibodies of JSC «Biomed» im. I. I. Mechnikov. Results and discussion. In Russia, improving the surveillance system for diphtheria continues to be an urgent task of the private epidemiology of this infection. The data obtained during the study allowed us to characterize the population immunity of the population of the Russian Federation, as a whole across the country, as sufficient to prevent the occurrence and spread of diphtheria. The main factor contributing to this was the long-term high coverage of vaccinations against diphtheria of persons in the decreed age groups (more than 95% of those vaccinated from the number of persons to be vaccinated in each age group). When comparing the level of immunization of the population depending on age, it was found that the percentage of vaccinated persons in the age group of people 50 years and older was statistically significantly lower than in the group of people younger than 50 years. The data of serological studies in Russia as a whole showed a high proportion of people with protective titers of antibodies to diphtheria in each age group – 3–4 years – 96.7 ± 0.1%, 15–17 years – 98.3 ± 0.1%, 18–29 years – 96,0 ± 0,4% – 97,5 ± 0,3%, 30–39 – 95,9 ± 0,4% – 97,5 ± 0.3%, 40–49 years old – 95,7 ± 0,4% – 97,7 ± 0,3%. The largest proportion of seronegative individuals is detected among groups aged 50–59 years and 60 years and older. The analysis of the share of seronegative persons in certain subjects of the Russian Federation revealed that the number of territories with a share of seronegative persons of more than 10% in the age groups of 50–59 years and 60 years and older was significantly higher than in other age groups. Conclusion. Thus, when planning companies for «сatch-up» immunization, it is advisable to provide mandatory revaccination of seronegative persons over 50 years of age. Timely revaccination according to the National Vaccination Calendar, tracking the proportion of persons susceptible to diphtheria in all indicator groups, followed by revaccination of seronegative persons in older ages will allow maintaining a high level of population immunity (more than 95%) and ensuring a consistently low incidence of diphtheria in the country for many years.

The paper presents data on measles cases identified in 18 provinces of South Vietnam (SV) in 2020, during the active phase of the pandemic of the new coronavirus SARS-CoV2. The measles virus actively circulated in SV in the first months of 2020: the average measles incidence rate was 1.27 per 100,000 population. Children under 5 years of age dominated in the age structure (71%). The vast majority of cases are people who have not been vaccinated against measles, as well as people who do not have information about vaccinations; in total, their share was 97.4%, but there were vaccinated and revaccinated individuals among the sick. Significantly more often, IgM-measles antibodies were recorded in samples obtained from the city of Can Tho, (n=57) where the infectious diseases hospital is located, receiving patients from neighboring regions of the SV. The largest number of measles cases were also recorded in the provinces of Dong Thap (n=57), Hao Glang (n=62) and Ho Chi Minh City (n=15). That is, residents of large cities, industrial and the medical centers were primarily involved in the measles epidemic process. A sharp decrease in the incidence of measles has been shown since April 2020, when measures to limit the spread of COVID-19 were introduced in SV. It should be noted that violations of vaccination associated with the COVID-19 pandemic, after the lifting of sanitary and epidemiological restrictions, may lead to increased morbidity and the development of measles outbreaks in Vietnam and other countries involved in the pandemic. Therefore, preventing future outbreaks will require strengthening measles surveillance and control measures to achieve its elimination.

Relevance. In the Russian Federation, despite the low incidence rate in 2020–2021, there are subjects where the incidence rate of meningococcal infection (MI) exceeds the national average by 2–9 times. MI often becomes fulminant with an extremely rapid development of symptoms up to infectious and toxic shock, which limits the possibility of providing specialized care. Less than 24 hours may pass between the appearance of the first symptoms (nonspecific, similar to ARVI) and the development of shock with a fatal outcome. To date, the most reliable way to protect against meningococcal infection is vaccination. However, the healthcare system until 2022 could use only one domestic vaccine with one serogroup A. Aims. To study the safety, reactogenicity and immunological efficacy of Meningococcal A+C polysaccharide vaccine, manufactured by Microgen, Russia, when used in persons aged 18 to 60 years. Materials and methods. The study included 100 people aged 18–60 years who met the inclusion criteria, the average age of the participants was 31.09 ±1.13 years. All study participants were evenly divided into two groups. The Meningo A+C® vaccine, Sanofi Pasteur, France (hereinafter referred to as MPV2 AC) was used as a comparison. PHA study was carried out using the test system «A set of diagnostic reagents for erythrocyte meningococcal polysaccharide groups A, B, C liquid according to TS 9388-004-68925985-10» manufactured by Bio-Diagnostics LLC, Russia (registration certificate No. FSR 2011/11185 dated 17.10.2011). Results and discussion. The results of the study assessing the reactogenicity and safety of the vaccine: in the first 7 days after vaccination, reactions were registered in 12.0% (95% CI: 5.62–23.80%) vaccinated with Meningococcal A+C polysaccharide vaccine, and in 10.0% (95% CI: 4.35–21.36%) in the comparison group, vaccinated with MPV2 AS. There was no statistically significant difference between the groups (p ≥ 0.05). Results of the study assessing the immunogenicity: on the 28^th day after single-dose immunization of the participants of the clinical trial, both in the group vaccinated with Meningococcal A+C polysaccharide vaccine, and in the control group (vaccinated with MPV2 AC), a statistically significant increase in antibody titer was noted, p ≤ 0.001: 76.0% (95% CI: 62.59–85.70%) versus 74.0% (95% CI: 60.45–84.13%) in the control group, χ2 =0.0533 and p=0.818.. Conclusions. Meningococcal A+C polysaccharide vaccine is characterized by safety, low reactogenicity and high immunogenicity comparable to the MPV2 AC vaccine.

The review discusses and confirms the important role of vaccination of patients with comorbid conditions against pneumococcus, influenza and meningococcus in the context of the COVID-19 pandemic. There are two main mechanisms of influence of preventive immunization on the course of the fight against the pandemic; by reducing the incidence of preventable infections and reducing the burden on healthcare, and by directly influencing the vaccines used on the infection processes with the SARS-Cov-2 virus and the pathogenetic mechanisms of COVID-19. Information is also provided on the vaccines used and their use, in particular in the context of the COVID-19 pandemic.

Relevance. The pandemic of a new coronavirus infection has become an unprecedented challenge for modern society. It took the entire population of the Earth by surprise, changing the lives of millions of people in the world in record time. Governments of different countries have reacted differently to the pandemic. The list of preventive measures and the timeliness of their adoption differed. Comparing and evaluating the experience of different countries and emergency response systems will help in the future to use best practices and models to combat future biological threats. The aim of the study was to identify and describe the features of the manifestation of the COVID-19 epidemic process in a number of countries, taking into account the ongoing anti-epidemic and preventive measures, and to hypothesize about the main factors that could potentially influence the differences in the manifestation of the COVID-19 epidemic process. Materials and methods. The choice of countries was conditioned by the purpose to compare the manifestations of epidemic process in our country with the great powers and economies of the world - USA and China and countries (Republic of Belarus and Sweden), which did not introduce lockdown and did not follow all WHO recommendations. To achieve this goal, a descriptive research method was used based on open source data, an analysis of relevant Russian and foreign literature was carried out (scientific electronic libraries PubMed and Elibrary; open sources of statistical information: Yandex DataLens Public: Coronavirus: Dashboard, Johns Hopkins University website, United Nations Population Division, World Bank, Global Panel Database on COVID-19 Pandemic Policy (Oxford COVID-19 Government Response Tracker), as well as the website of the World Health Organization (WHO), Our World in Data, Rospotrebnadzor and some media). Conclusion. The lowest incidence rate is observed in China (on average 315.1 per 100 thousand population [95% CI 314.8–315.4]), and the highest is in the USA (9957.7 per 100 thousand population [95% CI 9954.5–9960.9]). In terms of the number of tests conducted, the United States and Russia are in the lead. To date, the highest vaccination coverage and vaccination rate are observed in the PRC and amount to 92.4% and 90.1%, respectively. In general, these indicators do not reach 95% in all countries, which requires improving the quality of immunoprophylaxis measures. Anti-epidemic measures in the studied countries differed in their set, scope and severity of implementation. In China, Russia and the USA were held in full, and in Belarus and Sweden only partially, some of the events were not held at all. Thanks to the rapid creation of effective vaccines in Russia and China, it was possible to delay the onset of pronounced increases in morbidity at a later date, which, in turn, helped to reduce the burden on the healthcare system. At the same time, despite the obvious relevance of COVID-19, the question of a comprehensive study of the alleged risk factors (biological, social and natural) is still open. There is a certain probability that the virus will now be permanently present in the global population (it will become a seasonal disease).

Relevance. In 2007, WHO recommended pneumococcal conjugate vaccines (PCV) be included in national immunization schedules for young children. By 2020, 145 countries, including Russia, were using PCV. Aims. To identify vaccines with high epidemiological and immunological efficacy against various forms of pneumococcal infection, including carriage. Conclusions. It has been shown that PCV has high epidemiological and immunological efficacy against various forms of pneumococcal infection, including carriage. It was revealed that the mass use of PCV, leading to the elimination of "vaccine" serotypes, is simultaneously accompanied by the spread of cases of infection due to serotypes not included in vaccines, which significantly reduces the positive effect of vaccination. This requires frequent replacement of serotype polysaccharides in the vaccine in accordance with the serotypes of circulating strains. An alternative to PCV can be vaccines based on pneumolysin, surface pneumococcal proteins, whole – cell and live attenuated, protein-based subunit vaccines, etc. vaccine variants.

Teaching the discipline «Epidemiology» to foreign students is associated with certain difficulties due to both the lack of equivalents in the English language of terms and concepts used in Russia and the historically established difference in approaches to studying the occurrence and spread of diseases in human society. Schematically, in English-language literature and textbooks on epidemiology, the process of the occurrence of diseases is described on the model of the epidemiological triangle, in Russian literature – historically on the model of the epidemic process, the founder of the doctrine of which is L.V. Gromashevsky. The epidemiological triad is represented by the interaction of a human host, agent and environment – the basis of the epidemic process are 3 elements: the source of infection, the transmission mechanism and the susceptible organism. At first glance, the model of the epidemic process and the epidemiological triangle are somewhat similar. However, the model of the epidemic process according to L.V. Gromashevsky more clearly indicates the population level of the phenomenon, and the epidemiological triangle pays more attention /emphasis on the properties of the pathogen and its interaction with the human body (the level of organism) in the external environment. Teaching in the section «General epidemiology of infectious diseases» teaching about the epidemic process for foreign students is advisable to build from universal models such as the epidemiological triad, harmoniously combining the epidemiology of infectious and non-communicable diseases, followed by the separation of these concepts and the introduction of specific terminology adopted in Russia (source of infection, epidemic focus, transmission mechanism, transmission pathways). At the same time, along with non- communicable diseases, the processes of the spread of infections associated with the provision of medical care, sapronoses are most significantly illustrated with the help of an epidemiological triangle.