Results of comparative assessment of level of antibodies of IgG to SARS-CoV-2 in dynamics at standard and complex methods of treatment with use of medicinal peptide medicine of a timus of a timalin for patients with COVID-19 are presented in article. It was found that as a result of standard treatment, patients showed a decrease in antibody levels by 53% after 104 days. The addition of thymalin to standard therapy slowed down the decline of this indicator. So, a similar indicator in patients who took thymalin was only 21%. This contributed to maintaining strained adaptive immunity. The detected immunomodulatory properties of the preparation of thymalin with respect to COVID-19 can be reflected both in the formation of an effective immune layer of the population through natural immunization, and in the process of antibody formation during vaccination of target contingents.