The specifics of individual immune reactions after COVID-19 have not been studied sufficiently. This study aimed to describe the changes in indicators of cellular and humoral levels of immunity after COVID-19, and gage general trends and individual characteristics. We sampled blood of 125 unvaccinated COVID-19 patients (29 men and 96 women, median age 53 years) 1 to 4 months after recovery, and determined the relative content of T-lymphocytes (CD3⁺), B-lymphocytes (CD19⁺), and cells with late activation markers (CD3⁺HLA^–DR⁺) in them using flow cytometry. With the help of ELISA, we have registered the level of circulating immune complexes, which can be medium molecular weight (CICmed) and low molecular weight (CIClow), and the content of antibodies to SARS-CoV-2. In the mild course group, significant differences from the normal values (p < 0.001) were found for T cells (growth, 74.4 ± 1.2% vs. 68.6 ± 1.1%) and B cells (decline, 10.2 ± 0.7% vs. 13.9 ± 0.9%). In the moderately severe course and severe course groups, the level of CD3⁺HLA–DR⁺ lymphocytes was increased (7.7 ± 0.4% and 15.7 ± 2.5%, respectively, versus 3.9 ± 0.8% in the control group; p < 0.01). All the examined patients had high levels of CIClow (2.6-2.9-fold increase) and CICmed (1.6–1.8-fold increase). The protective level of antibodies to SARS-CoV-2 above 150 BAU/ml was registered in about 50% of the mild group participants, 75% of the moderately severe group members, and 100% of patients who had the disease in a severe form. We detected no connections between immune disorders and clinical features of the course of the disease and the period thereafter, with the exception of abdominal syndrome peculiar to the acute stage of the disease. The article also describes a clinical case of detection in the early post-COVID-19 period of a pathological clone characteristic of B cell chronic lymphocytic leukemia, and its subsequent disappearance and normalization of the immunophenotype as registered during a follow-up 1.5 years after recovery. The persistent immunological shifts should be taken into account when assessing the risks of reinfection and possible complications.