Phase II, observer-blind, randomized study on the safety, reactogenicity, immunogenicity and impact on intestinal shedding of a single dose of monovalent high-dose inactivated poliovirus type 2 vaccine (m-IPV2 HD) or a single dose of standard trivalent inactivated poliovirus vaccine (t-IPV) when given concomitantly with the third dose of bivalent oral poliovirus vaccine (b-OPV) to infants early in life

Inclusion Criteria:

1. Age: 6 weeks (-7 to +14 days).
2. Healthy without obvious medical conditions that preclude the subject to be in the study as established by the medical history and physical examination.
3. Written informed consent obtained from 1 or 2 parents or legal guardian as per Panama regulations.

Exclusion Criteria:

1. Previous vaccination against poliovirus.
2. Low birth weight (BW <2,500 gm).
3. Any confirmed or suspected immunosuppressive or immunodeficient condition including human immunodeficiency virus (HIV) infection.
4. Family history of congenital or hereditary immunodeficiency.
5. Major congenital defects or serious uncontrolled chronic illness (neurologic, pulmonary, gastrointestinal, hepatic, renal, or endocrine).
6. Known allergy to any component of the study vaccines.
7. Uncontrolled coagulopathy or blood disorder contraindicating intramuscular injections.
8. Administration of immunoglobulins and/or any blood products since birth or planned administration during the study period.
9. Acute severe febrile illness at day of vaccination deemed by the Investigator to be a contraindication for vaccination (the child can be included at a later time if within age window and all in/exclusion criteria are met.).
10. Member of the subject's household (living in the same house or apartment unit) has received OPV in the last 3 months.
11. Subject who, in the opinion of the Investigator, is unlikely to comply with the protocol or is inappropriate to be included in the study for the safety or the benefit-risk ratio of the subject.