Fractional Inactivated Poliovirus Vaccine Booster and Rotavirus Study (fIPV)

With the switch from trivalent to bivalent oral poliovirus vaccine (OPV) in 2016, the Global Polio Eradication Initiative (GPEI) is recommending inactivated poliovirus vaccine (IPV) use as one of the potential strategies to respond to outbreaks of type 2 wild type and/or circulating vaccine-derived polioviruses. However, the current global inactivated poliovirus vaccine (IPV; 0.5 mL, full-dose) supply shortage dramatically limits the number of doses available for an effective outbreak response. Therefore, GPEI has proposed use of intradermal administration of a booster of fractional IPV (fIPV; 0.1 mL, one-fifth the full-dose) as a dose-sparing strategy to increase the number of children vaccinated and stretch IPV supplies. No study has compared immunogenicity of a fIPV booster in children previously vaccinated with a single IPV. Furthermore, the IPV shortage has led to reconsideration of fIPV use in routine immunization programs. Previous studies found that in one and two dose head-to-head comparisons, fIPV induced a lower proportion of seroconversion and antibody responses than IPV. However, recent studies of seroconversion and priming suggest two fIPV given at least eight weeks apart may be more immunogenic than one IPV. Because of these findings and the global IPV shortage, the most recent WHO position paper suggests that countries consider administering two fIPV at 6 and 14 weeks of age as an alternative to one IPV after the OPV2 cessation in April 2016. However, no trial has conducted a direct comparison of the immunogenicity of IPV at 14 weeks of age with that of fIPV at 6 and 14 weeks of age.

The immunogenicity of rotavirus (RV) vaccines will also be assessed when given concomitantly with IPV/fIPV. Currently, WHO recommends either of two licensed, live attenuated oral rotavirus vaccines for all children worldwide: the pentavalent RotaTeq (RV5) and monovalent Rotarix (RV1). Many lower income countries where IPV is being introduced are also poised to introduce rotavirus vaccine in the coming years. The first dose of OPV interferes with RV vaccines and RV vaccines may be more immunogenic when delivered with IPV compared with OPV. The proposed study presents an opportunity to compare the two and three dose responses of RV1 and RV5 when delivered with IPV compared with previous studies in Bangladesh when co-administered with OPV.

In addition, recent studies have suggested that host genetic factors (i.e., Secretor status and Lewis and salivary ABO blood group phenotype) mediate susceptibility to rotavirus infection. More precisely, non-secretors (i.e., children lacking a functional fucosyl transferse-2 [FUT2] gene) have substantially reduced risk of rotavirus infection of certain genotypes. Furthermore, certain rotavirus genotypes infected mainly Lewis negative children, independent of secretor status. In addition, blood group antigen status has been proposed to be associated with infection (or lack of infection) by particular rotavirus genotypes. The proposed trial will assess whether Secretor status, Lewis and salivary ABO blood group phenotype are also associated with vaccine response.