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Despite the rapid accumulation of facts about the humoral immune response in COVID-19, there are still no evidencebased answers to questions about the factors influencing the level and duration of the detection period of antibodies to SARS-CoV-2 in the blood.Objective: To assess the prevalence, clinical and demographic associations of IgG antibodies to RBD of the SARSCoV-2 spike protein at different times after COVID-19.Materials and methods. Residents of the Altai region of Russia, Caucasians aged 20-93 years, who had COVID-19 from May 2020 to February 2021 (n = 314), took part in a onetime observational study. The level of antibodies in the blood was measured by enzyme-linked immunosorbent assay 1-14 months after the onset of the clinical manifestation of COVID-19.Results. Anti-RBD IgG antibodies of the SARS-CoV-2 spike protein were detected in 86.9% of the study participants. The dependence of the antibody titer on the duration of the period after COVID-19 was not revealed. The antibody titer was positively correlated with the complication of COVID-19 pneumonia and the volume of lung tissue lesions. The presence of pneumonia COVID-19 and the volume of lung tissue lesions are positively associated with age. Age positively correlated with antibody titer regardless of the pneumonia COVID-19 in the anamnesis.Conclusion. IgG antibodies to RBD of the SARS-CoV-2 spike protein are present in most of the COVID-19 patients. The titer of these antibodies in adults depends on age, complications of pneumonia COVID-19, and probably persists up to 14 months after the first symptoms of infection appear.

The aim of the study is to determine the clinical and epidemiological features of measles in the Altai territory. Materials and methods: a retrospective analysis of 92 medical histories of inpatient patients with a confirmed diagnosis of «Measles» at the age of 17 to 54 years, who were treated in the Infectious Departments of City Hospitals № 5 and №11 in Barnaul in 2015–2018, was made. Results: the epidemic situation of measles in the Altai territory is characterized by an increase of morbidity rate in 2015, as well as isolated cases in 2017–2018. The peculiarity of the outbreak of the disease was in-hospital infection of patients upon admission to medical hospitals and late diagnosis of measles, as well as the importation of infection from adjacent territories (regions of Russia and the Republic of Kazakhstan), which is confirmed by genotyping of the virus in patients. The development of the disease in 23,9% of those,who were vaccinated, was routinely observed in the age group older than 30 years. In the clinical picture of measles at the present stage, along with the classical manifestations, in 15.2% of patients in the first days of the disease gastroenteritis was marked, in 40,2% of patients the signs of hepatitis (cytolysis syndrome) were observed. Conclusion: the prevalence among the patientspersons, older than 30 years, may indicate the extinction of post-vaccination immunity. Timely immunization against measles in adulthood (after 30 years), will increase the effectiveness of measures to implement the program of elimination of measles in the Altai territory. The development of gastroenteritis up to the 5 days of the disease (on average 2,5±0.9 days), hepatitis in the period of height of the disease (in 15,2% and 40,2% of patients, respectively), determined the erroneous diagnosis of «Enterovirus infection», pseudotuberculosis, etc. and deserved the attention of practitioners.