In the light of the switch from OPV to IPV and the continued presence of cVDPV2 in many countries, it is important to understand and quantify the impact of IPV on pharyngeal mucosal immunity, to inform whether and to what extent the mucosal and humoral immune response following IPV could reduce transmission and spread.~This study will assess the effect of vaccination with IPV in parallel with poliovirus type-2 naïve infants (infants having received bOPV) on the pharyngeal and fecal shedding and the induction of immunity following type-2 poliovirus challenge. This understanding would provide critical information on the potential use of IPV in specific settings to interrupt transmission / reduce spread. The results from this study may potentially have important consequences on public health policy in countries which use IPV for infant priming, as they will help to show the extent to which a type-2 mucosal immunity gap remains following a primary series of IPV.
The study will compare the poliovirus type-2 pharyngeal mucosal excretion in the first week, and at 2 and 4 weeks following the administration of a challenge novel OPV2 (nOPV2) dose at 18 weeks of age in 2 parallel groups of infants