Antibody responses and symptoms after DTP and either tetanus or diphtheria Haemophilus influenzae type B conjugate vaccines given for primary immunisation by separate or mixed injection

The safety and immunogenicity of two conjugate Haemophilus influenzae type B (Hib) vaccines administered either mixed with, or in separate limbs to, a whole-cell DTP vaccine, was compared in infants vaccinated at 2, 3 and 4 months of age. Antibody titres to purified polyribosylribitol phosphate, diphtheria, and to pertussis antigens between infants who received the Hib and DPT vaccines in separate limbs or in the same limbs were similar (P>0.1) while antibody titres to tetanus toxoid were higher in the later group (P<0.05). This study demonstrated that both Hib vaccines can be mixed with whole-cell DTP vaccine without reducing immunogenicity of either vaccine or increasing the incidence of adverse reactions.