BACKGROUND: Diagnosis and treatment of COVID-19 in patients with primary immunodeficiency, or inborn errors of immunity, are often challenging. AIM: Description of the COVID-19 course and therapy of adult patients with primary immunodeficiency treated in medical organizations of Moscow Healthcare Department. MATERIALS AND METHODS: We analyzed a cohort of 68 patients over 18 years (median ― 35 years) with primary immunodeficiency; 91% of patients have primary immunodeficiency with predominantly antibody deficiencies. Altogether 90 cases of the new СOVID-19 were analyzed: in 68 cases infection occurred for the first time, in 22 cases it recurred. The duration of the disease ranged from 3 to 80 days. Duration of PCR-positivity ranged from 0 to 59 days, median 8 days. RESULTS: Patients with Wuhan and Delta strains had more severe inflammatory signs according to C-reactive protein and lactate dehydrogenase, in patients with Wuhan lung involvement on CT-scam was larger. In demonstrated group of patients higher C-reactive protein correlated with larger lung involvement, longer duration of the disease and PCR-positivity, significant lymphopenia also correlated with higher C-reactive protein. To our data regularity of intravenous immunoglobulin therapy and IgG trough level didn’t correlate with infection severity and duration of the disease and virus-carriage. Indirectly, the change in the spectrum of medicine used in patients of the analyzed group coincided with the virus strain evolution. Anti-inflammatory therapy was mainly presented by dexamethasone and antagonists to interleukin 6 or its receptor (anti-IL-6): 55% and 73% for Wuhan, 63% and 50% for Delta, 17% and 39% for Omicron. Then, preference was gradually given to the target anti-cytokine medicine. Etiotropic antiviral therapy was more often used to treat infection caused by Wuhan and Delta strains ― 32% and 38%, respectively (in 17% for Omicron). With shifting toward immunotherapy by specific against COVID-19 immunoglobulins and monoclonal antibody to SARS-CoV-2: 5% and 9% for Wuhan, 0% and 75% for Delta, 48% and 83% for Omicron, respectively. Immune and etiotropic therapy was not carried out in Wuhan in 39%, in Delta in 43%, in Omicron in 41% of cases. The overall mortality rate from COVID-19 in the analyzed group was 3%. CONCLUSION: Patients with primary immunodeficiency represent a vulnerable group to the SARS-CoV-2 virus with a high risk of not only severe, but also a protracted and undulating course of infection, what must be taken into account for the correct interpretation of the patient's condition and the timely administration of the appropriate therapy.