Immunogenicity and Safety of Sabin Strain Inactivated Poliovirus Vaccine Booster Dose Administered Separately or Concomitantly with Inactivated Hepatitis A Vaccine or Measles-Mumps-Rubella Combined Attenuated Live Vaccine: An Open-labelled, Randomized, Controlled, Phase 4 Clinical Trial

Objectives To determine whether a Sabin-strain inactivated poliovirus booster (sIPV) given concomitantly (same day, different sites) with MMRV or inactivated hepatitis A vaccine (HepA) is non-inferior in immunogenicity and comparable in safety to separate administration at the 18-month visit. Methods Open-label, randomized Phase IV trial in healthy children (18 months + 4), allocated 2:2:2:1:1 to sIPV&MMRV, sIPV&HepA, sIPV-only, MMRV-only, or HepA-only. Primary endpoints were Day-30 seroconversion rates (SCRs) for poliovirus types 1–3 (sIPV arms) and for HepA (HepA arms). Results Of 892 screened, 889 were randomized; baseline characteristics were balanced. By Day 30, seroprotection was 100% for PV types 1–3 in all sIPV-containing arms. SCRs were high and similar across concomitant vs separate administration; all pairwise SCR differences met non-inferiority (−10% margin). Adjusted post-vaccination GMTs were comparable across serotypes. For HepA, Day-30 SPoR was 99.3% vs 100.0% and adjusted GMC 412.2 vs 465.9 (P=0.2224). For MMRV, Day-30 SPoR was 100% in both groups with similar adjusted GMCs. Within 30 days, overall adverse reactions were 14.5% / 17.4% / 16.3% / 7.3% / 10.8% (sIPV&MMRV / sIPV&HepA / sIPV-only / MMRV-only / HepA-only), mostly mild–moderate; no vaccine-related SAEs. (NCT06442449) Conclusions Same-day sIPV co-administration with MMRV or HepA was non-inferior and well tolerated, supporting programmatic adoption.