Monovalent Oral Poliovirus Vaccine Type 1 Intestinal and Humoral Immunity Study

Inclusion Criteria: * Healthy infants 5 weeks of age (range: 35-41 days). * Parents that consent for participation in the full length of the study. * Parents that are able to understand and comply with planned study procedures. Exclusion Criteria: * Parents and infants who are unable to participate in the full length of the study. * A diagnosis or suspicion of immunodeficiency disorder either in the infant or in an immediate family member. * A diagnosis or suspicion of bleeding disorder that would contraindicate parenteral administration of fIPV or collection of blood by venipuncture. * Evidence of a chronic medical condition identified by a study medical officer during physical exam. * Infection or illness at the enrolment visit (i.e., 5 weeks of age) that a study medical officer judges would prevent the start of study activities at 6 weeks of age (i.e., blood collection and vaccination). * Receipt of any polio vaccine (OPV or IPV/fIPV) before enrolment based upon documentation or parental recall. * Known allergy/sensitivity or reaction to polio vaccine, or its contents. * Infants from multiple births. Infants from multiple births will be excluded because the infant(s) who is/are not enrolled would likely receive OPV through routine immunization and transmit vaccine poliovirus to the enrolled infant. * Infants from premature births (\<37 weeks of gestation).