A Study to Evaluate the Safety and Immunogenicity of Monovalent OPV2 in Children Aged 1 to 5 Years in Lithuania

Inclusion Criteria: 1. 1 to 5 years of age, previously vaccinated with three or four doses of IPV. 2. Healthy without obvious medical conditions that preclude entry of the subject into the study as established by the medical history and physical examination. 3. Written informed consent obtained from 1 or 2 parent(s) or legal guardian(s) as per country regulations. Exclusion Criteria: 1. Previous vaccination against poliovirus outside the national immunization schedule. 2. Any confirmed or suspected immunosuppressive or known immunodeficient condition including human immunodeficiency virus (HIV) infection. 3. Family history of congenital or hereditary immunodeficiency. 4. Major congenital defects or serious uncontrolled chronic illness (neurologic, pulmonary, gastrointestinal, hepatic, renal, or endocrine). 5. Known allergy to any component of the study vaccines or to any antibiotics. 6. Administration of immunoglobulins and/or any blood products since birth or planned administration during the study period. 7. 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.). 8. Member of the subject's household (living in the same house or apartment unit) has received OPV in the last 3 months. 9. 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.