This multicentered, 12-arm phase 2 study will be the first pediatric evaluation of nOPV3 in healthy young children, infants, and newborns. This trial will be initiated once results in the adult phase 1 study of nOPV3 indicate that there are no safety concerns, and that the vaccine elicits demonstrable immunogenicity. Additionally, prior to enrolling into cohort 2, the adult phase 1 data must show no concerning signals of reversion of attenuating sites from a subset of Next Generation Sequencing.~This study is intended to provide critical data on safety, immunogenicity, and genetic stability, as well as to demonstrate the vaccine's ability to reduce fecal shedding following a challenge with the Sabin type 3 strain.~Enrollment in this pediatric study will be staggered into three age-descending cohorts of 6 treatment groups of escalated target dose levels for the nOPV3 vaccine: cohort 1 composed of 192 healthy young children 1 to <5 years of age who have completed their full routine polio immunization series; cohort 2 composed of 860 healthy infants 6 weeks of age not previously vaccinated (OPV/IPV) who will be primed with a dose of inactivated poliomyelitis vaccine (IPV) prior to OPV3 vaccination [a subset, of the infants (n=360) will also receive the challenge virus]; and cohort 3, composed of 480 healthy poliomyelitis unvaccinated neonates (day of birth +3 days).~Progression into the next cohort and groups within cohorts will depend on safety evaluations of the prior Phase 1 adult trial and Day 8 safety evaluation of the previous groups in prior cohorts in the study.
The purpose of this clinical trial is to assess the safety and tolerability (primary objective), immunogenicity (primary and secondary objectives), fecal shedding of vaccine viruses (secondary objective) and the potential for neurovirulence of shed virus (secondary objective) of a novel oral polio type 3 vaccine, nOPV3, as compared to Sabin monovalent type 3 vaccine controls (mOPV3), in healthy young children (192 subjects), infants (860 subjects), and neonates (480 subjects).