COMBINATION OF DTP AND HAEMOPHILUS-INFLUENZAE TYPE-B CONJUGATE VACCINES CAN AFFECT LABORATORY EVALUATION OF POTENCY AND IMMUNOGENICITY

A commonly used Diphtheria-Tetanus-Pertussis (whole-cell) vaccine was combined with each of three different Haemophilus influenzae type b (H ib) capsular polysaccharide vaccines. Each Hib vaccine incorporated on e of three different protein conjugates: tetanus toroid, diphtheria CR M(197) toroid or group B Neisseria meningitidis outer membrane vesicle s. The effects of these combinations on the subsequent laboratory cont rol testing were examined. The addition of the Hib vaccines had no sig nificant effect on the reactogenicity or the potency of the whole-cell pertussis component. The potency of, and antibody responses to, the d iphtheria component were also unaffected in all three combinations. Ho wever, combination with the Hib vaccine comprising polysaccharide conj ugated to tetanus toroid had dramatic effects on tetanus potency and i mmunogenicity when assayed in mice. This combination resulted in a fiv e-fold potentiation of the tetanus potency and a similarly large incre ase in the antibody responses to tetanus toxin and toroid. The level o f the antibody response to the Hib polysaccharide in this vaccine was also elevated, more than 20-fold, as a result of the combination. Such phenomena were not evident with combinations involving the other two Hib vaccines. These results have implications for the control testing of combined vaccines containing a whole-cell pertussis component and H ib polysaccharide-tetanus protein conjugate vaccine.