Change in anti-SARS-CoV-2 IgG antibodies (COVID-19) among the population of the Russian Federation regions and in convalescents in dynamics

Materials and methods. The article presents the results of laboratory tests for the presence of IgG antibodies to the SARS-CoV-2 coronavirus in 2112 patients living in 5 regions of the Russian Federation. In the main group of the study, 50 people were under dynamic observation for 6 months. Depending on the severity, the main group was divided into two subgroups: group I1 (n=25), represented by patients with moderate coronavirus infection, and group I2 (n=25), consisting of patients with a severe course of coronavirus infection. Blood sampling was carried out on the 14th day of illness (from the moment the first symptoms appeared) in the conditions of the procedure room of the Infectious Diseases Clinical Hospital №1, subsequent blood sampling (44 and 74 days, 3–6 months). Results. During a three-month observation of patients in the main group, there were no significant changes in the content of IgG antibodies to the SARS-CoV-2 coronavirus, and all fluctuations were characterized only by a trend. By the 4th month of observation, the decrease in antibody titer relative to the maximum level (as a rule, 14–44 days) was 43.3% in subgroup I1, and 37.6% in subgroup I2. By the 5th month, the level of IgG antibodies to the SARS-CoV-2 coronavirus in sub-group I1 was 40.9% relative to the maximum value (on day 44), and in subgroup I2 – 35.0% relative to the maximum value (on day 14). After 6 months from the start of observation, the content of IgG antibodies to the SARS-CoV-2 coronavirus in both groups did not differ significantly from the control (p>0,05). Conclusion. We found that there were no significant changes in the level of IgG antibodies to the SARS-CoV-2 coronavirus from the 14th day of illness to the 3rd month of observation from the moment of the first symptoms of the disease. Starting from the 4th month of observation, the level of antibodies decreased in both groups by multiples in relation to the maximum values, decreasing by the 6th month of observation to the values of the control group.