Randomized Controlled Clinical Trial of bivalent Oral Poliovirus Vaccine and Inactivated Poliovirus Vaccine in Nigerian Children.

Background We conducted a trial in Nigeria to assess the immunogenicity of the new bOPV + IPV immunization schedule and gains in type 2 immunity with addition of second dose of IPV. The trial was conducted in August 2016-March 2017 period, well past the tOPV-bOPV switch in April 2016. Methods This was an open-label, two-arm, non-inferiority, multi-center, randomized controlled trial. We enrolled 572 infants of age ≤14 days and randomized them into two arms. Arm A received bOPV at birth, 6 and 10 weeks, bOPV+IPV at week 14 and IPV at week 18. Arm B received IPV each at 6, 10, 14 weeks and bOPV at 18 weeks of age. Results Seroconversion rates for poliovirus types 1 and 3, respectively, were 98.9% (95%CI:96.7-99.8) and 98.1% (95%CI:88.2-94.8) in Arm A, and 89.6% (95%CI:85.4-93.0) and 98.5% (95%CI:96.3-99.6) in Arm B. Type 2 seroconversion with one dose IPV in Arm A was 72.0% (95%CI:66.2-77.3), which increased significantly with addition of second dose to 95.9% (95%CI:92.8-97.9). Conclusion This first trial on the new EPI schedule in a sub-Saharan African country demonstrated excellent immunogenicity against poliovirus types 1 and 3, and substantial/enhanced immunogenicity against poliovirus type 2 after 1 to 2 doses of IPV respectively.