Immunogenicity and safety of an adjuvanted inactivated polio vaccine, IPV-Al, in primary and booster trials in Asia, Central America and Europe

Abstract

Background: Withdrawal of OPV and the widespread introduction of IPV is key in the Polio Endgame Strategy. This transition from OPV to IPV requires more and affordable IPV in quantities sufficient to secure at least two doses of IPV for every child. An adjuvanted inactivated polio vaccine (IPV-Al), obtained by adsorption of a reduced dose of inactivated poliovirus to an aluminium hydroxide adjuvant, can help mitigate global supply and cost constraints of IPV through dose-sparing. Aim: Investigation of immunogenicity and safety of IPV-Al compared to standard IPV: Methods and materials: Two primary vaccination phase 3 trials in infants vaccinated at 6, 10, 14 weeks and 9 months in the Philippines; at 2, 4, 6 months and 15–18 months in Panama. A Phase 2 primary vaccination trial in the Dominican Republic in infants vaccinated at 6, 10, 14 weeks. A Phase 1/2 booster vaccination trial in Denmark in children and adolescents (10–15 years) with a history of standard IPV vaccination. Results: Seroconversion rates (an antibody titre ≥4-fold higher than the estimated maternal antibody titre and a titre ≥8) evaluated one month after primary vaccination were: polio type 1, 96–98% (IPV-Al) versus 99–100% (IPV); type 2, 94–100% versus 99–100%; and type 3, 98–99% versus 99–100%. Non-inferiority of IPV-Al to IPV (predefined 10%-point margin) was confirmed in trials assessing primary immunogenicity. In infants, robust booster responses were demonstrated following a fourth polio vaccination and post-booster geometric mean titres (GMTs) were higher than post-priming GMTs. In the adolescent trial, robust booster responses were demonstrated following a fifth polio vaccination. IPV-Al was well tolerated with a safety profile comparable to that of standard IPV in the three trials. Conclusion: IPV-Al was demonstrated to be non-inferior to standard IPV for seroconversion following primary vaccination in the EPI schedule in Philippines and Dominican Republic, and at 2, 4, 6 months in Panama. Robust post-booster responses in 9-month-olds, 15–18-month-olds and 10–15-year-olds were demonstrated for IPV-Al. IPV-Al was safe and well tolerated. Results support the applicability of the dose-sparing adjuvanted IPV-Al vaccine to help secure a more affordable and stable supply of IPV for prevention of poliomyelitis as part of the global polio eradication initiative.