SAFETY AND IMMUNOGENICITY OF HAEMOPHILUS-INFLUENZAE TYPE-B-NEISSERIA-MENINGITIDIS GROUP-B OUTER-MEMBRANE PROTEIN COMPLEX CONJUGATE VACCINE MIXED IN THE SYRINGE WITH DIPHTHERIA-TETANUS-PERTUSSIS VACCINE IN YOUNG GAMBIAN INFANTS

To ensure compliance and to reduce costs it is important, especially i n less developed countries, that programs of child immunization should require as few clinic attendances and as few injections as possible. Therefore we have investigated whether a Haemophilus influenzae type b conjugate vaccine could be given safely and effectively with diphther ia-tetanus-pertussis vaccine (DTP). One hundred twenty-six Gambian inf ants were given both polyribosylribitol phosphate (PRP)-outer membrane protein complex (PedvaxHIB(R)) and DTP on the same day at 8, 12 and 1 6 weeks of age; 60 were given the vaccines mixed in the syringe and 66 were given the vaccines separately. To minimize the injection volume the dose of PRP-OMPC used in both groups was 7.5 mug, which is half th e usual dose. There were no significant differences in anti-PRP antibo dy titers between the groups after 1, 2 or 3 doses. The geometric mean titers of antibody for the two groups combined were 0.29 mug/ml 1 mon th after the first dose, 1.03 mug/ml after the second dose and 1.11 mu g/ml after the third dose. Concentrations of antibodies to diphtheria, tetanus and pertussis 1 month after the third dose were not significa ntly different between the two groups. Systemic side effects were repo rted with equal frequency in the two groups and were similar to those reported elsewhere for DTP. Tenderness at the injection site was more common where the combined injection (0.75 ml) had been given than wher e DTP alone (0.5 ml) had been given. The main drawback to the use of t hese 2 vaccines together is the complexity of the mixing procedure use d in this clinical trial.