SAFETY AND IMMUNOGENICITY IN YOUNG INFANTS OF HAEMOPHILUS-B TETANUS PROTEIN CONJUGATE VACCINE, MIXED IN THE SAME SYRINGE WITH DIPHTHERIA-TETANUS-PERTUSSIS-ENHANCED INACTIVATED POLIOVIRUS VACCINE

Because inactivated poliovirus vaccine (IPV) and Haemophilus influenza e b vaccine are advised in many programs and may be incorporated furth er in other programs, we undertook a study to determine whether the ad ministration of a tetravalent preparation of diphtheria-tetanus-pertus sis-IPV mixed in one syringe with tetanus-conjugate H. influenzae b va ccine (DTP-IPV-PRPT) is associated with increased reactogenicity or in terference with immunogenicity of individual vaccine components. In a placebo-controlled, double blind study, a total of 161 infants were en rolled (80 DTP-IPV-PRPT and 81 DTP-IPV-placebo), Vaccine was administe red at 2, 4 and B months of age. Oral poliovirus vaccine was added at 7 months of age and a booster of oral poliovirus vaccine and DTP-IPV w as also administered at 12 months of age, according to the policy in I srael. Local and systemic side effects were similar in both groups exc ept for irritability after the second dose and use of acetaminophen wh ich we observed slightly but significantly more often in the DTP-IPV-P RPT recipients. After the third dose the geometric mean titers of anti -polyribosyl-ribitol phosphate antibodies were 3.7 and 0.05 mu g/ml in the PRPT and placebo groups, respectively (P < 0.001). Higher tetanus antitoxin titers were observed among recipients of DPT-IPV-placebo (1 .1 IU/ml vs. 0.7 IU/ml, P = 0.003). A similar trend was found for pert ussis agglutinin titers (93.4 vs. 65.4, P = 0.054). No difference was observed for anti-diphtheria toroid and poliovirus 1, 2 and 3. Protect ive titers against diphtheria and tetanus (greater than or equal to 0. 02 IU/ml) after the third dose mere demonstrated in greater than or eq ual to 99% of all infants. At 18 months of age (6 months after the DTP -IPV booster) no significant difference between the groups was demonst rated showing good priming for all components, although the trend for lower anti-tetanus antibodies was still present. We conclude that alth ough a mild, clinically insignificant interference occurred for some c omponents after the primary series, no interference with priming was s hown and that DTP-IPV mixed with PRPT is safe and immunogenic in young infants.