A Clinical Study Comparing Safety and Immunogenicity of bOPV of Bilthoven Biologicals

Inclusion Criteria: 1. Normal healthy children of both sexes of age 5 to 6 years (60-83 months) at the time of vaccination and who have received at least 3 doses of trivalent oral polio vaccine (tOPV) based upon documentation (Study Part 1). 2. Normal healthy infants of both sexes of age 6-8 weeks (42-56 days) at the time of the first vaccination and have not received oral polio vaccine (OPV) previously based upon documentation (Study Part 2). 3. Parents/legal guardians of participants willing to give written informed consent and willing to comply with study protocol. 4. Free of obvious health problems as established by medical history and screening evaluation including clinical examination. 5. Resident of study area. Exclusion Criteria: 1. Participation in another clinical trial in the 4 weeks preceding the (first) trial vaccination or planned participation in another clinical trial during the present trial period. 2. A diagnosis or suspicion of congenital or acquired immunodeficiency disorder, malignancy, receiving immunosuppressive therapy such as systemic corticosteroids therapy for a period of ≥ 1 week either in the participant or in an immediate family member. 3. A diagnosis or suspicion of bleeding disorder that would contraindicate collection of blood by venipuncture. 4. Acute or persistent diarrhea (defined as diarrhea that lasts 14 days or longer), infection or illness at the time of enrollment (6-8 weeks of age) that would require participant's admission to a hospital or would contraindicate provision of OPV. 5. Acute vomiting and intolerance to liquids within 24 hours before the enrollment visit. 6. Infants from multiple births (i.e. twins). 7. History of allergy or systemic hypersensitivity to any of the vaccine components or history of a life-threatening reaction to the study vaccines or a vaccine containing the same substances. 8. Chronic illness at a stage that could interfere with trial conduct or completion. 9. Planned administration/ administration of a vaccine not foreseen by the study protocol during the study period with the exception of routine Expanded Program on Immunization (EPI) program vaccines including pneumococcal vaccine, and rotavirus vaccine (Polio vaccines are not allowed during the study period). 10. Blood or blood-derived products received in the past. 11. Any vaccination one week preceding the trial vaccination. 12. Presence of significant malnutrition (\< -3 standard deviation \[SD\] weight for length) or acute or chronic, clinically significant pulmonary, endocrine, autoimmune, cardiovascular, metabolic, hepatic or renal functional abnormality, as determined by medical history, and physical examination, which in the opinion of the investigator, might interfere with the study objectives 13. History of any neurological disorder or history of seizure (febrile or afebrile), or encephalopathy, encephalitis, hypotonic-hyporesponsive episode. 14. Febrile illness or acute illness on the day of inclusion is temporary exclusion criterion. 15. Participant with any other condition, which, in the opinion of the investigator would jeopardize the safety or rights of the participant participating in the study or making it unlikely the participant, could complete the protocol.