Evaluate Immunogenicity, Safety, and Reactogenicity of Rotavac® in Healthy Infants Aged Between 6-8 Weeks in Vietnam

Inclusion Criteria: * Healthy infants as established by medical history and clinical examination before entering the study. * Age: 6-8 weeks * Weight ≥ 2.5kg at birth. * Infants received EPI vaccines at birth (i.e., OPV, BCG and/or Hep B) * Parental ability and willingness to provide informed consent. * Parent who intends to remain in the area with the participant during the study period. Exclusion Criteria: * Presence of diarrhea or vomiting in the previous 72 hours or on the day of enrollment (temporary exclusion). * Presence of fever (temperature ≥37.5oC) or hypothermia (temperature ≤35.5oC) on the day of enrollment (temporary exclusion). * Concurrent participation in another clinical trial. * Presence of significant malnutrition or any systemic disorder (cardiovascular, pulmonary, hepatic, renal, gastrointestinal, hematological, endocrine, immunological, dermatological, neurological, cancer or autoimmune disease) as determined by medical history and/or physical examination which would compromise the infant's health or is likely to result in non-conformance to the protocol. * History of congenital abdominal disorders, intussusception, abdominal surgery * Known or suspected impairment of immunological function based on medical history and physical examination. * Prior receipt of rotavirus vaccine. * A known sensitivity or allergy to any components of the study medication. * Major congenital or genetic defect. * Participant's parents not able, available or willing to accept active follow-up by the study staff. * Has received any immunoglobulin therapy and/or blood products since birth or planned administration during the study period. * History of chronic administration (defined as more than 14 days) of immunosuppressants including corticosteroids. Infants on inhaled or topical steroids may be permitted to participate in the study. * History of any neurologic disorders or seizures. * Any medical condition in the parents/infants that, in the judgment of the investigator, would interfere with or serves as a contraindication to protocol adherence or a participant's parent's/legally acceptable representative's ability to give informed consent.