Objective: To study the immunological effectiveness of inactivated poliomyelitis vaccine (IPV) for children's primary vaccination in China and to compare with the oral poliomyelitis vaccine (OPV) used in routine vaccination.
Methods: The 2-month-old children were randomly immunized with IPV and OPV, with 208 subjects in each group. The pre- and post-vaccination blood samples were collected. Micro-neutralization method was used to measure the antibody response against 3 types of polioviruses. chi2 test was used to evaluate the statistical difference of protection rates between two groups, while the antibody titers were transformed by logarithm and analyzed by Z-test. P < 0.05 was always used to define the significance of analysis.
Results: After 3 doses of immunization, the protection rates in IPV group reached to 100.0% (186/186), 97.3% (181/186), 98.9% (184/186) for poliovirus type 1, 2, 3, respectively, and in OPV group were 97.4% (188/193), 100.0% (193/193), 95.3% (184/193), respectively. The geometry mean titers (GMTs) were 151.2, 86.7, 211.3 for IPV group; and 1089.5, 538.2, 203.7 for OPV group. IPV showed comparable protection rates with OPV for type 1 and 2 (chi2(I) = 2.991, P = 0.084; chi2(II) = 3.512, P = 0.061), while type 3 was higher than OPV (chi2(III) = 4.143, P = 0.042). The GMT of type 1 and 2 in IPV group were lower than OPV group (Z(I) = 12.537, P = 0.000; Z(II) = 13.415, P = 0.000), while the GMT of type 3 were comparable in two groups (Z(III) = 0.067, P = 0.947).
Conclusion: IPV showed roughly comparable immunological effectiveness in young children. The protection rates for type 1 and 2 were similar to OPV, while type 3 was higher than in OPV group; In terms of GMT,type 1 and 2 in IPV group were lower than OPV, but type 3 were comparable to OPV group.