Introduction. Morbidity and mortality of COVID-19 actualizes the identification of groups with the greatest risk of primary and re-infection, persons in need of priority vaccination or revaccination.Objective. To study the factors affecting the content of IgG antibodies to the S-protein SARS-CoV-2 in convalescents after suffering COVID-19 for 6 months.Materials and methods. The study of the Military Medical Academy and the Helix Laboratory Service was carried out from 06/01/2020 to 08/01/2021 on the basis of the Military Medical Academy and the Helix centers. The study included 1421 people – both sexes from 18 to 70 years old. 1205 with asymptomatic and mild disease (outpatient group). 216 with moderate or severe form (inpatient group). The outpatient group underwent a quantitative determination of IgG to the spike (S) protein SARS-CoV-2 by immunochemiluminescence analysis at 30, 45, 60, 90, 180 days from diagnosis. The diagnosis was verified by a positive RT-PCR result. The inpatient group underwent an identical study on the 1st, 14th, 45th, 60th, 90th and 180th days from the moment of admission to the hospital. The diagnosis was verified in the same way.Results. In convalescents, post-infectious immunity is formed from 30 days. Older age was associated with a more pronounced production of IgG to the S-protein SARS-CoV-2, mainly in older women. Moderate and severe course is characterized by higher concentrations of IgG to the SARS-CoV-2 S protein. A high level of IgG to the S-protein SARS-CoV-2 persists for up to 90 days, with a subsequent decrease by 180 days. Body weight, days of oxygen therapy, hyperthermia, the volume of lung tissue lesions and the level of C-reactive protein correlate with the concentration of IgG to the S-protein SARS-CoV-2. The use of glucocorticoids (GCS) is characterized by the presence of a higher concentration of IgG to the S-protein SARS-CoV-2 up to 6 months. There is a dose-dependent effect of using GCS.Conclusion. The formation and maintenance of the level of neutralizing antibodies for 6 months depends on the severity of the disease, the gender and age of the patients, and the fact of using GCS. This must be taken into account when carrying out therapeutic and preventive measures, planning vaccination.

The development of laboratory diagnostics is carried out not only by technological modernization, but also by the expansion of the volume of non-invasive studies with the active participation of patients in the collection of biomaterials. According to the results of the study with 68 patients the most effective verification of SARS-CoV-2 is carried out with the active participation of the patient in the collection of biomaterials. Increasing the information content of research is being developed by methods of logical analysis, which allow obtaining new knowledge about the subject area.

Objective: to assess the climatic and seasonal characteristics of vitamin D status in the population of different cities of the Russian Federation.Material and methods. The study was conducted from September 2014 to June 2018. Surveyed 104321 serum of patients (one hundred four thousand three hundred twenty-one) of the 105 cities of the Russian Federation. Of them women: 80738, which was 77.4% of men 23583 - 22,6%. To determine the concentration of 25(OH)D in serum electrochemiluminescent method was used. The analysis was performed on the automatic analyzer Cobas 8000 (Switzerland).Results. The concentration of calcidiol (25 (OH) D) in patients living in cities located in different climategeographic regions of the Russian Federation varied from 3.0 to 536.10 ng/ml. the Average concentration of 25(OH) D was the lowest in Makhachkala (19.26 ± 0.53 ng/ml), the maximum in Surgut (42.5 ± 0.44 ng/ml). Only 18% of the cities average concentration of 25(OH)D reached the lower limit of positive level of 30 ng/ml. More than half of the patients (60,1-81.7 per cent) of all regions, the concentration of 25(OH)D was below normal - less than 30 ng/ml. Vitamin d deficiency (<20 ng / ml) was found in almost a third of the Russian population (24.1-65.7%). The statistically significant highest level of 25(OH)D was detected in the autumn months (30,30 ± 0,30 ng/ml), and the lowest - in the spring (27,11 ± 0,25 ng/ml). The frequency of serum detection, where calcidiol concentration was lower than normal (<30 ng/ml), even in autumn was observed in more than half (57.5%) of the entire population.Conclusion. Thus, the data indicate a serious deficiency and even deficiency of vitamin D in the population of the Russian Federation. Us there is no correlation between the average level of vitamin D in the blood serum and the geographical latitude of the settlement. However, the dependence of the concentration of 25 (OH) D on the time of year, when the patient's blood is taken for analysis.

Objective: to assess the climatic and seasonal characteristics of vitamin D status in the population of different cities of the Russian Federation. Material and methods . The study was conducted from September 2014 to June 2018. Surveyed 104321 serum of patients (one hundred four thousand three hundred twenty-one) of the 105 cities of the Russian Federation. Of them women: 80738, which was 77.4% of men 23583 - 22,6%. To determine the concentration of 25(OH)D in serum electrochemiluminescent method was used. The analysis was performed on the automatic analyzer Cobas 8000 (Switzerland). Results . The concentration of calcidiol (25 (OH) D) in patients living in cities located in different climategeographic regions of the Russian Federation varied from 3.0 to 536.10 ng/ml. the Average concentration of 25(OH) D was the lowest in Makhachkala (19.26 ± 0.53 ng/ml), the maximum in Surgut (42.5 ± 0.44 ng/ml). Only 18% of the cities average concentration of 25(OH)D reached the lower limit of positive level of 30 ng/ml. More than half of the patients (60,1-81.7 per cent) of all regions, the concentration of 25(OH)D was below normal - less than 30 ng/ml. Vitamin d deficiency (<20 ng / ml) was found in almost a third of the Russian population (24.1-65.7%). The statistically significant highest level of 25(OH)D was detected in the autumn months (30,30 ± 0,30 ng/ml), and the lowest - in the spring (27,11 ± 0,25 ng/ml). The frequency of serum detection, where calcidiol concentration was lower than normal (<30 ng/ml), even in autumn was observed in more than half (57.5%) of the entire population. Conclusion . Thus, the data indicate a serious deficiency and even deficiency of vitamin D in the population of the Russian Federation. Us there is no correlation between the average level of vitamin D in the blood serum and the geographical latitude of the settlement. However, the dependence of the concentration of 25 (OH) D on the time of year, when the patient's blood is taken for analysis.