After three years of the outbreak of Coronavirus Disease 2019 (COVID-19) pandemic, main tasks as to treatment and vaccination are still pending their solution. Today, it is known that SARS-CoV 2 coronaviruses are intracellular viral infections having an inevitable negative impact on all cells of the human body, including the blood cells. It is established that COVID-19 patients can be classified into mild, moderate, and severe. Modern literature does not describe ultrastructural changes of circulatory blood cells in patients with moderate course of this disease.