A randomized, controlled, blinded study of the safety and immunogenicity of Haemophilus influenzae type b conjugate vaccine injected at different intramuscular sites in Chinese infants.

To compare the safety and immunogenicity of Haemophilus influenzae type b (Hib) conjugate vaccine administered via the vastus lateralis and deltoid muscles, 320 healthy Chinese infants<12 mo of age were enrolled in a randomized, controlled, blinded study and divided into 2 age groups: 2-5 mo and 6-12 mo. Each age group was then randomized (1:1) to either the vastus lateralis (experimental) group who received Hib vaccination into this muscle 2 or 3 times at monthly intervals, or the deltoid (control) group who received Hib vaccination into this muscle either 3 times (2-5 mo group) or twice (6-12 mo group) at monthly intervals. Local and systemic adverse reactions after each vaccine dose were recorded, and Hib-PRP antibody concentrations were determined by ELISA at 28 d after completion of the immunization schedule. There were no significant differences in the proportions of subjects with post-immunization Hib-PRP antibody concentrations ≥1.0 μg/mL or ≥0.15 μg/mL with the two injection sites for either age group, or in the post-immunization Hib-PRP antibody concentrations achieved (P>0.05). In addition, there were no significant differences in the rates of local and systemic reactions after the first and second vaccinations between the 2 injection sites for either age group (P>0.05), but the rate of systemic reactions in the 2-5 mo group after the third vaccination via the vastus lateralis muscle was significantly lower than after deltoid vaccination (0% vs 8.57%; P<0.05). Thus, administration via the vastus lateralis muscle is worth considering for Hib vaccination.