Despite the mass population immunization, the total spread of the COVID-19 pandemic once again made scientists around the world doubt the effectiveness of currently existing methods of prevention and treatment of a novel coronavirus infection. The rationale for a potentially new approach to the preventive therapy of COVID-19 using probiotic bacterial strains was the presence of a bidirectional “gut-lung” axis, which interacts between these organs through transported soluble microbial metabolites in blood. The study aimed to determine the relationship between the correction of the gut microbiota with the polycomponent synbiotic Maxilac® and clinical and laboratory markers of the severity of the new coronavirus infection. During the open-label, prospective, observational study 60 patients with a confirmed diagnosis of COVID-19, a moderate severity and the presence of gastrointestinal symptoms were divided into 2 groups: the 1st performed the outpatient complex standard treatment with the addition of synbiotic, the 2nd - without addition. All patients of group 1 showed positive dynamics of clinical and laboratory indicators of COVID-19 severity, compared with group 2, where 2 patients needed hospitalization due to the aggravation of the course of novel coronavirus infection. A reduction in the duration of clinical symptoms and the duration of outpatient treatment was revealed in a group of patients taking Maxilac®. The dynamics of clinical and laboratory indicators reflecting the course of COVID-19 indicate the effectiveness of symbiotic’s usage as adjuvant therapy and the possibility of recommending its use in the complex treatment of patients with a novel coronavirus infection.