Abstract
BACKGROUND: Combination vaccines protecting against diphtheria, tetanus, pertussis, poliomyelitis, and Haemophilus influenzae type b reduce injection burden and improve compliance. While widely used globally, no domestically produced pentavalent vaccine is currently licensed in China. Recent updates to China's immunization schedule-including earlier initiation and an added booster for pertussis-highlight the need for compatible combination vaccines. This study evaluated the immunogenicity and feasibility of a novel DTacP-sIPV/Hib candidate vaccine in preclinical models. METHODS: The vaccine was assessed in NIH mice and Wistar rats. Two Hib dosages were tested in mice alongside a DTacP-wIPV/Hib vaccine (Pentaxim(®)). In rats, two sIPV formulations (Formulations A and B) were administered using different intervals (1-month vs. 2-month) and injection methods (mixed vs. separate). Antibody titers were measured by ELISA and poliovirus neutralization assays. RESULTS: The candidate vaccine elicited robust immune responses in both models. In mice, after three doses, the high-dose Hib group achieved >90% seroconversion for pertactin antigen, whereas the low-dose group reached 100% for all antigens. In rats, antibody responses after three doses were comparable to those induced by Pentaxim(®), with no significant differences between immunization schedules or administration routes. Compared with Formulation A (containing a higher type I sIPV antigen content), Formulation B exhibited reduced type I poliovirus neutralization after the first dose (p < 0.05) and delayed seroconversion, while responses to other antigens remained similar. CONCLUSION: The candidate DTacP-sIPV/Hib vaccine showed robust immunogenicity and flexibility across schedules and administration methods. A formulation including DT 12.5 Lf, TT 3.5 Lf, PT 25 μg, FHA 25 μg, PRN 8 μg, PRP 10 μg, and sIPV I/II/III at 30/32/45 DU is proposed for further development.