A Study of Immunogenicity and Seroconversion With Sabin IPV Schedules in China.

A Study of Immunogenicity and Seroconversion With Sabin Inactivated Polio Vaccine Schedules in China.

In April 2017, WHO recommended that a two-dose, Inactivated Poliovirus Vaccine, IPV-only schedule at 4 months and 8 months of age can be used after polio eradication, with a schedule seroconversion target of at least 90%. However, there is no such data for China domestic Sabin strain IPVs to support a 2-dose schedule among Chinese infants. This research is to determine the seroconversion rates among two arms: Group 1: two-dose schedule, infants will be received two doses of Sabin IPV, the first dose at 4 month of age, and the second dose at 8-11 month of age. Group 2: three-dose schedule, infants will be received three doses of Sabin IPV at 2, 3 and 4 month of age respectively. This schedule is currently recommended by manufacture's package insert for routine use. The hypothesis is the seroconversion will be above 90% in both groups.

As a part of global polio eradication endgame immunization strategy, WHO requested all OPV-using countries to introduce at least one dose of IPV into the routine immunization schedule. Ideally IPV should be administered after 14 weeks of age, however an IPV-OPV sequential schedule is acceptable if VAPP is a concern. China stopped trivalent OPV in routine immunization in May 2016, introduced one dose of IPV at 2 months followed by three doses of type I / III bivalent OPV (bOPV) at 3 and 4 months and 4 years. A Sabin strain IPV was licensed in January 2015, and a second Sabin IPV was approved by China FDA in September 2017. The production capacity will increase in the next few years and will meet the demands of an IPV-only schedule in China. Other Sabin IPVs are in clinical trial stages, which will lead to sufficient IPV production for China to export IPV. In April 2017, WHO/SAGE recommended that a two-dose, IPV-only schedule can be used after polio eradication, with a schedule seroconversion target of at least 90%. The recommendation was based in part on a study conducted in Cuba using Salk-IPV at 4 months and 8 months of age. Considering that risk of polio virus transmission is decreasing over time, and that IPV - either domestic Sabin-IPV or imported Salk-IPV - is expensive (6 USD/dose) for a program serving a birth cohort of 18 million, an efficient two-dose, IPV-only schedule will be very competitive with a more traditional 4-dose IPV-only schedule. However, for domestic Sabin IPVs, there are no such data to support a 2-dose schedule among Chinese infants. The overall objective of this research is to determine the seroconversion rates of two reduced Sabin IPV schedules in Chinese children - a 2-dose schedule and a 3-dose schedule. Group 1: two-dose schedule, infants will be received two doses of Sabin IPV, the first dose at 4 month of age, and the second dose at 8-11 month of age. Group 2: three-dose schedule, infants will be received three doses of Sabin IPV at 2, 3 and 4 month of age respectively. This schedule is currently recommended by manufacture's package insert for routine use. The hypothesis is the seroconversion will be above 90% in both groups.

Subjects vaccinate Sabin IPV at 2, 3, and 4 months of age,will be collected blood specimens twice - right before the first dose of IPV, and one month after the 3rd dose of IPV.

Subjects vaccinate first dose IPV at 4 months, and the second dose IPV given between 8 and 11 months of age,will be collected blood specimens twice - right before the first dose of IPV, and one month after the 2nd dose of IPV.

We select one Sabin IPV product, produced by Kunming Bio institute, which is available for China's National Immunization Program in the selected study sites.

Determine whether the seroconversion rate is above 90% using a two-dose Sabin IPV alone schedule with the first dose Sabin IPV given at 4 months and the second dose Sabin IPV given ≥4 months after the first dose.

Measure neutralizing antibody titers against poliovirus type I, II and III among two-dose Sabin IPV-only schedules compared with three-dose Sabin IPV alone schedule.

Inclusion Criteria: Parent or legal guardian agree to participate in our study. The family is living locally with legal residency status. Exclusion Criteria: Parent or legal guardian does not agree to participate in our study. The potential subject has received IPV or OPV before 4 months of age in the two-dose schedule group. The potential subject has one or more contraindications to IPV (although we will note the contraindications).