Population immunity to the three serotypes of poliovirus post-interruption of wild poliovirus transmission in Nigeria.

The presence of neutralizing antibodies is considered a surrogate marker of protection against the three serotypes of poliovirus. The need to use the Microneutralization test in assessing the neutralizing antibodies to the three serotypes of polioviruses among vaccinated children aged 1-15 years informed this study. Of 400 children tested, 309 (77.3 %), 253 (63.3 %), and 308 (77.0 %) had neutralizing antibodies against P1, P2, and P3, respectively. Only 191 (47.8 %) had neutralizing antibodies against P1P2P3 simultaneously, the global target. Whilst 91 (22.8 %) had no neutralizing antibodies against P1, these children were protected against P2 (23.0 %) and P3 (43.9 %). Similarly, 147 (36.8 %) children had no neutralizing antibodies against P2, but were protected against P1 (66.0 %) and P3 (65.3 %). Furthermore, 52(13 %), 51(12.8 %), and 52 (13.0 %) had no neutralizing antibodies against the combination of P1P3, P1P2, and P2P3, respectively. Only 34 (8.5 %) of the children had no nAb to any of the three serotypes. The optimal number of Polio vaccine doses for effective immunity varied depending on the serotype. Also, gender differences may favor the speed at which children achieve the target antibody titers. Higher antibody titers (1:1280) were observed for P2 and P3, with six of the children having a titer of 1:10240 for P3. The combination of supplementary immunization activities and routine immunization generated a robust immune response across all poliovirus serotypes, in contrast to each of the two. The administrative data and population immunity were not commensurate. New strategies to increase immunity against the P1P2P3 simultaneously in all age groups are urgently required.