Evaluate Immunogenicity, Safety, and Reactogenicity of Rotavac in Healthy Infants in Vietnam

Inclusion Criteria 1. Healthy infants as established by medical history and clinical examination 2. Age: 6-8 weeks 3. Weight ≥2.5kgs at birth 4. Infants receiving EPI vaccines as per Vietnam immunization program 5. Parental ability and willingness to provide informed consent. 6. Parent who intends to remain in the area with the participant during the study period. Exclusion Criteria: 1. Presence of diarrhea or vomiting in the previous 72 hours or on the day of enrollment (temporary exclusion). 2. Presence of fever (\>37.5C) or hypothermia (\<35.5C) on the day of enrollment (temporary exclusion). 3. Concurrent participation in another clinical trial. 4. Presence of significant malnutrition or any systemic disorder (cardiovascular, pulmonary, hepatic, renal, gastrointestinal, haematological, endocrine, immuno-logical, dermatological, neurological, cancer or autoimmune disease) as determined by medical history and/or physical examination which would compromise the child's health or is likely to result in non-conformance to the protocol. 5. History of congenital abdominal disorders, intussusception, abdominal surgery 6. Known or suspected impairment of immunological function based on medical history and physical examination. 7. Prior receipt of rotavirus vaccine. 8. A known sensitivity or allergy to any components of the study vaccines. 9. Major congenital or genetic defect. 10. Participant's parents not able, available or willing to accept active follow-up by the study staff. 11. Has received any immunoglobulin therapy and/or blood products since birth or planned administration during the study period. 12. History of chronic administration (defined as more than 14 days) of immunosuppressant including corticosteroids. Infants on inhaled or topical steroids may be permitted to participate in the study. 13. History of any neurologic disorders or seizures. 14. 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.