Inactivated polio vaccines from three different manufacturers have equivalent safety and immunogenicity when given as 1 or 2 additional doses after bivalent OPV: Results from a randomized controlled trial in Latin America

Background: Since April 2016 inactivated poliovirus vaccine (IPV) has been the only routine source of polio type 2 protection worldwide. With IPV supply constraints, data on comparability of immunogenicity and safety will be important to optimally utilize available supplies from different manufacturers. Methods: In this multicenter phase IV study, 900 Latin American infants randomly assigned to six study groups received three doses of bOPV at 6, 10 and 14 weeks and either one IPV dose at 14 weeks (groups SP-1, GSK-1 and BBio-1) or two IPV doses at 14 and 36 weeks (groups SP-2, GSK-2 and BBio-2) from three different manufacturers. Children were challenged with mOPV2 at either 18 (one IPV dose) or 40 weeks (two IPV doses) and stools were collected weekly for 4 weeks to assess viral shedding. Serum neutralizing antibodies were measured at various time points pre and post vaccination. Serious adverse events and important medical events (SAE and IME) were monitored for 6 months after last study vaccine. Results: At week 18, 4 weeks after one dose of IPV, overall type 2 seroconversion rates were 80.4%, 80.4% and 73.3% for SP-1, GSK-1 and BBio-1 groups, respectively; and 92.6%, 96.8% and 88.0% in those who were seronegative before IPV administration. At 40 weeks, 4 weeks after a second IPV dose, type 2 seroconversion rates were ≥99% for any of the three manufacturers. There were no significant differences in fecal shedding index endpoint (SIE) after one or two IPV doses (SP: 2.3 [95% CI: 2.1–2.6]); GSK: 2.2 [1.7–2.5]; BBio 1.8 [1.5–2.3]. All vaccines appeared safe, with no vaccine-related SAE or IME. Conclusion: Current WHO prequalified IPV vaccines are safe and induce similar humoral and intestinal immunity after one or two doses.