Immunogenicity and safety of different sequential schedules of Sabin strain-based inactivated poliovirus vaccination: A randomized, controlled, open-label, phase IV clinical trial in China

Background: The immunogenicity and safety of the sequential schedule of Sabin strain-based inactivated poliovirus vaccine (sIPV) and bivalent oral poliovirus vaccine (bOPV) remains poorly understood in Chinese population.

Methods: A multi-center, open-label, randomized controlled trial was performed involving 648 healthy infants aged 2 months from Inner Mongolia, Shanxi, and Hebei provinces. These participants were divided into three groups: sIPV-bOPV-bOPV, sIPV-sIPV-bOPV, and sIPV-sIPV-sIPV. Doses were administered sequentially at age 2, 3, and 4 months. Neutralisation assays were tested using sera collected at 2 months and 5 months.

Results: A total of 569 were included in the per-protocol analysis. The seroconversion rates of poliovirus type 1 and 3 were 100% in all three groups, the seroconversion rate of poliovirus type 2 was 91.53% (173/189) (95% CI: 86.62-95.08) in the sIPV-bOPV-bOPV group, 98.38% (182/185) (95% CI: 95.33-99.66) in the sIPV-sIPV-bOPV group, and 99.49% (194/195) (95% CI: 97.18-99.99) in the sIPV-sIPV-sIPV group. For the seroconversion rate of poliovirus types 1 and 3, the sIPV-bOPV-bOPV and sIPV-sIPV-bOPV groups were non-inferior to the sIPV-sIPV-sIPV group. For the seroconversion rate of poliovirus type 2, the sIPV-sIPV-bOPV group was non-inferior to the sIPV-sIPV-sIPV group, and the sIPV-bOPV-bOPV group was inferior to the sIPV-sIPV-sIPV group. All three groups exhibited good safety, with two serious adverse events reported, that were unrelated to vaccine.

Conclusions: In china, a new vaccination schedule that including 2 doses of IPV in the national immunization programs is essential. Trial registration ClinicalTrials.govNCT04054492.