Immunogenicity and safety of sequential Sabin strain inactivated poliovirus vaccine from different manufacturers in infants: Randomized, blinded, controlled trial.

Objectives: The National Immunization Program allows using a different manufacturer's vaccine for follow-up doses when the same vaccine is unavailable. This study aimed to evaluate the safety and immunogenicity of administering a third dose of Sabin strain (sIPV) from a different manufacturer in infants who had previously received two doses of sIPV.

Methods: This randomized, blinded, controlled trial enrolled 200 healthy infants (≤12 months) to assess the safety and immunogenicity of sequential vaccination, who were randomly assigned to receive a third dose of sIPV from either a different manufacturer (experimental group) or the same manufacturer as the first two doses (control group). The study took place in Xiaogan City, Hubei Province, China, from 20 May 2024 to 6 September 2024. Immunogenicity and safety were assessed using per-protocol and safety populations, respectively.

Results: The seroconversion rates for poliovirus types 1, 2, and 3 were 79.52 %, 67.47 %, and 74.70 % in the experimental group, respectively, compared to 73.56 %, 49.43 %, and 63.22 % in the control group, with P-values of 0.360, 0.017, and 0.106, respectively. The most common systemic adverse event (AE) was fever, and no significant differences in the incidence of AEs between the two groups were observed. No serious adverse events related to vaccines were reported.

Conclusion: Sequential vaccination with sIPV from different manufacturers demonstrated superior immunogenicity compared to the initial vaccine, with no significant safety differences, indicating that using vaccines from different manufacturers for sequential dosing is a feasible and effective option.