Neutralizing Activity of Vaccine-Induced Antibodies Against Vaccine-Derived Polioviruses Type 2

Background: Nowadays, poliomyelitis caused by wild polioviruses (PVs) has been virtually eradicated. However, since the removal of the type 2 component from the oral polio vaccine (OPV), immunity to PV2 has declined despite expansion of the use of the inactivated polio vaccine (IPV). Unfortunately, sources of neurovirulent PV2 remain in the world in the form of vaccine-derived poliovirus type 2 (VDPV2) cases and outbreaks and immunodeficient iVDPV2 excretors. Methods: Neutralizing antibodies (nABs) in sera from children with different numbers of IPV/OPV doses were evaluated against VDPV2 strains. Results: A genetic analysis of four VDPV2 strains with varying genetic divergence from Sabin 2 (4.32–17.39%) revealed a number of mutations in antigenic sites. We observed that 6.5–51.8% of undervaccinated (1–2IPV) children did not have nABs against at least one studied VDPV2. Fully vaccinated children showed almost 100% neutralization, although 3.1% vaccinated with 3IPV did not have nABs against three VDPVs; 4.5% vaccinated with 3IPV + 1bOPV and 2.5% vaccinated with 5tOPV did not have nABs against the most divergent iVDPV2 strain. Conclusions: Therefore, some fully vaccinated children may not have detectable levels of protective nABs against VDPV2.