Given that COVID-19 is a global public health problem and that almost all countries in the world have been severely affected by the COVID-19 pandemic, research is being actively pursued to better understand the effects of the virus on human cells. However, it is not clear what changes are observed in the cells of the main gate of infection – the mucosa of the mouth and the nose at different clinical forms and at different periods of disease. Understanding the ultra-structural cell changes of SARS-CoV-2 targets may help clarify the pathogenic aspects of infection in the lower respiratory tract. In this study, the elements of the life cycle of SARS-CoV-2 virus in the cells of the respiratory epithelium of the nose in patients with COVID-19 were evaluated using electron microscopy for the purpose of detecting the peculiarities of viral activity depending on the form and period of disease. Bioptats of the nasal mucous membrane were taken from COVID-19 patients and subsequently examined by electron microscopy. The severity of structural changes in tissue samples, presence of SARSCoV-2 virus in cells were determined, then bioptats were grouped according to the clinical form of the infection process (inapparent, acute upper respiratory tract infections, viral lung disease) and period of disease. It has been established that the most characteristic changes in the mucous membrane of the nose were observed in the first week of infection caused by SARS-CoV-2 and occurring in the form of acute respiratory disease, while viral lung infections have had the highest virus density in vesicles within cells, the formation of smooth virus-free vesicles is most common in inapparent forms. The data obtained may indicate that the formation of classical virus-induced changes in the respiratory epithelium of the nose mucous (vesicles with viral particles and signs of their release from the cell) is characteristic of localized forms of infection caused by SARS-CoV-2 (respiratory infection of the upper respiratory tract) and in cases of generalized infection (viral infection of the lungs and probably other organs and systems) accumulation of the infectious agent in high concentrations in vesicles.

The recent vaccination campaign targeting the new coronavirus infection (COVID-19) carried out in the Armed Forces of the Russian Federation, on the background of the current unstable global pandemic situation, makes it necessary to study post-vaccination population immunity to the SARS-CoV-2 virus and thus identify key features of immunity in organized military collectives. In the future, this will make it possible to objectively assess the risks of a worsening pandemic situation, effectively adjust the ongoing sanitary and anti-epidemic measures aimed at preserving and strengthening the health of military personnel, as one of the main conditions for maintaining the combat readiness of the Armed Forces of the Russian Federation. During a study conducted on epidemic indications, it was found that vaccination with Gam-Covid-Vac contributes to the formation of collective immunity with 95% effectiveness. A gender-based analysis of the immune response showed that the proportion of persons who lack class G immunoglobulins to SARS-CoV-2 among females is twice than that among men (9.3% and 4.7%, respectively). Seroprevalence indicators, classified by blood group, range from 94.4% (AB (IV) Rh) to 97.4% (A (II) Rh). There were no significant differences in seroprevalence between groups of people with different blood groups; however, the highest value of seroprevalence was seen among military personnel with blood group A (II) Rh. In this context, it is advisable to continue monitoring the formation of immunity in individuals with various blood groups. The results obtained made it possible to form a primary medical and social portrait of a serviceman with the most adequate immune response to the introduction of the Gam-Covid-Vac vaccine (a man under the age of 20 with blood type A (II) Rh) and to draw a conclusion about the high effectiveness of vaccination in military units (formations) staffed by conscripts and military educational organizations.