Safety and Immunogenicity of a Sabin Strain-Based Inactivated Polio Vaccine: A Phase III, Randomized, Blinded, Positive-Control Clinical Trial in Infants Aged Two Months

Objectives: This randomized, blinded, positive-controlled phase III clinical trial aims to evaluate the safety and immunogenicity of the Sabin strain-based inactivated polio vaccine (sIPV) produced by Biominhai in healthy infants after primary and booster immunization. Methods: A total of 1200 healthy infants, aged 2 months, were randomly assigned to two groups in a 1:1 ratio to receive either one dose of sIPV or the control wIPV at 2, 3, and 4 months of age, followed by a booster dose at 18 months. The safety and immunogenicity of both the primary and the booster immunization were assessed. Results: The incidence of adverse reactions (AEs) was significantly lower in the sIPV group compared to the wIPV group after the primary immunization. Specifically, redness was the most frequently reported AE, occurring in 9% of the sIPV group versus 14% in wIPV (p = 0.01). Diarrhea was also less common in the sIPV group (3%) compared to the wIPV group (8%, p = 0.0004). Moreover, there were no significant differences in incidence, severity, or symptoms of AEs between the groups after the booster immunization. Most AEs were classified as grade 1, and notably, no serious AEs (SAEs) were associated with the trial vaccine. Seroconversion rates for types 1, 2, and 3 poliovirus neutralizing antibodies, in the sIPV group, exceeded 98% at 30 days after primary immunization and remained above 90% at 30 days after booster immunization. Notably, seroconversion rates for all three serotypes following both primary and booster immunizations were non-inferior to those observed in the wIPV group. Additionally, the geometric mean titers (GMTs) of neutralizing antibodies against all types were significantly higher in the sIPV group. Conclusions: The sIPV produced by Biominhai demonstrated comparable safety and immunogenicity to the control vaccine after both primary and booster immunizations.