Inclusion Criteria:  Healthy male or female children at the age of 2 months at the time of the first vaccination with PI / PS, vaccinated according to age by the schedule of the National Calendar of Preventive Vaccinations of the Russian Federation; Baby should be ≥ 37 weeks gestational age and birth weight ≥ 2500 g; Children who do not have contraindications for vaccination (by the Protocol, according to medical history and clinical examination); An Informed Consent Form for participation in the research, voluntarily and personally signed by the parent / adoptive parent of the child, before any of the research procedures; Ability, in the researcher's opinion, of the parents / adoptive parents of the child to comply with the requirements of the Protocol (attendance of all scheduled Visits, completion of the Child Observation Diary, etc.).  Exclusion Criteria:  Orphans (except for officially adopted children) and children without parental care; Child's gestational age <37 weeks and birth weight <2500 g; Participation in any other clinical study; Received or planned vaccination with any other rotavirus vaccine before enrollment in this study; A history of diarrhea or blood in the stool or a violation of bowel movements in the last 14 days; A history of chronic diseases of the gastrointestinal tract, history of intussusception of the intestine and congenital malformations of the gastrointestinal tract, predisposing to it, surgery on the abdominal organs; Known sensitivity or allergy to any of the PI and PS components; Serious post-vaccination reactions/complications disorders/defects associated with any previous vaccinations; Any significant systemic disease (from the lungs, liver, kidneys, skin, cardiovascular system, gastrointestinal tract, endocrine system, immune system, nervous system, and cancer or autoimmune disease) that would jeopardize children's health or result in non-compliance with the Protocol; Congenital or genetic disorders/defects; Clinically significant abnormalities in laboratory parameters that go beyond the limits of the normal range identified at the Screening and may have a negative impact on the safety of the child's participation in the study; Household contact with immunocompromised people or with an immunocompromised pregnant woman; In the researcher's opinion, the child is not eligible for inclusion in the study, or the researcher is convinced that the parent / adoptive parent will not follow the Protocol's procedures; Continuous use (more than 14 days from birth until inclusion in the study) of immunosuppressants or immunomodulators; Continuous use (more than 14 days from birth until inclusion in the study) of steroid drugs at a dose of more than 0.5 mg/kg/day in terms of prednisone. The use of topical or inhaled steroids is permitted; A history of proven hepatitis B, diphtheria, tetanus, whooping cough, poliomyelitis, hemophilic or pneumococcal infection; Confirmed or suspected immunodeficiency condition (based on medical history); Hereditary or congenital immunodeficiency (according to family history ); Administration of immunoglobulins or blood components from birth until inclusion and their planned administration during the study.