Abstract
In May 2016, countries using oral polio vaccine for routine immunization switched from trivalent oral poliovirus vaccine (tOPV) to bivalent type 1 and 3 OPV (bOPV). This was done in order to reduce risks from type 2 vaccine-derived polioviruses (VDPV2) and vaccine-associated paralytic poliomyelitis (VAPP) and to introduce ≥1 dose of inactivated poliovirus vaccine (IPV) to mitigate post-switch loss of type 2 immunity. We conducted a literature review of studies that assessed humoral and intestinal immunogenicity induced by the newly recommended schedules. Differences in seroconversion rates were closely associated with both timing of first IPV administration and number of doses administered. All studies demonstrated high levels of immunity for types 1 and 3 regardless of immunization schedule. When administered late in the primary series, a second dose of IPV closed the humoral immunity gap against polio type 2 associated with a single dose. IPV doses and administration schedules appear to have limited impact on type 2 excretion following challenge.
Highlights
The Global Polio Eradication Initiative is close to interrupting wild polio virus (WPV) transmission worldwide, with only 22 cases of type-1 WPV reported in 2017 [1]
Studies were previously known to the authors or found by searching the PubMed database using search terms related to bivalent type and oral poliovirus vaccine (OPV) (bOPV) and inactivated poliovirus vaccine (IPV)/fractional IPV regimens
Studies in Chile and China with IPV alone as the first dose followed by 2 bOPV doses achieved high type 1 and 3 seroconversion rates (>98%), but only 77.4% and 55.8% type 2 seroconversion, respectively
Summary
The Global Polio Eradication Initiative is close to interrupting wild polio virus (WPV) transmission worldwide, with only 22 cases of type-1 WPV reported in 2017 [1]. To achieve the goal of complete eradication of polio, it will be necessary to discontinue the use of all live, attenuated oral poliovirus vaccine (OPV) viruses that, in settings with low population immunity, have the potential to revert to neurovirulent circulating vaccine derived polioviruses (cVDPV). To mitigate ongoing risk from type 2 polioviruses, the World Health Organization (WHO) Strategic Advisory Group of Experts (SAGE) recommended including 1 or more inactivated poliovirus vaccine (IPV) doses in the new routine infant immunization schedules [4]. This review summarizes key data from recent studies, focusing on the impact of such schedules on type 2 immunity, to inform global polio immunization policy until all use of OPV can be discontinued
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