Safety and immunogenicity of inactivated poliovirus vaccine when given with measles–rubella combined vaccine and yellow fever vaccine and when given via different administration routes: a phase 4, randomised, non-inferiority trial in The Gambia

Methods We did a phase 4, randomised, non-inferiority trial at three periurban government clinics in west Gambia. Infants aged 9–10 months who had already received oral poliovirus vaccine were randomly assigned to receive the IPV, measles–rubella, and yellow fever vaccines, singularly or in combination. Separately, IPV was given as a full intramuscular or fractional intradermal dose by needle and syringe or disposable-syringe jet injector at a second visit. The primary outcomes were seroprevalence rates for poliovirus 4–6 weeks post-vaccination and the rate of seroconversion between baseline and post-vaccination serum samples for measles, rubella, and yellow fever; and the post-vaccination antibody titres generated against each component of the vaccines. We did a per-protocol analysis with a non-inferiority margin of 10% for poliovirus seroprevalence and measles, rubella, and yellow fever seroconversion, and (1⁄3) log2 for log2-transformed antibody titres. This trial is registered with ClinicalTrials.gov, number NCT01847872.