CAN HAEMOPHILUS-INFLUENZAE TYPE-B TETANUS TOXOID CONJUGATE VACCINE BECOMBINED WITH DIPHTHERIA TOXOID PERTUSSIS-VACCINE TETANUS TOXOID

Objective: To assess the side effects and immune responses after three serial doses of PRP-T vaccine (a Haemophilus influenzae type b [Hib]- tetanus toxoid conjugate vaccine) given concurrently or mixed with ads orbed DPT vaccine (diphtheria toxoid-pertussis vaccine-tetanus toxoid) . Design: Multicentre randomized controlled trial. Setting: Four publi c health units in western Canada. Participants: Healthy infants 8 to 1 5 weeks old at entry who were able to receive routine primary vaccinat ions. Of 444 infants enrolled, 433 (98%) completed the study. Interven tions: All infants received PRP-T and DPT vaccines at 2, 4 and 6 month s of age: half received them mixed in one injection and the others as separate, bilateral injections. Main outcome measures: Side-effects 24 and 48 hours after each dose and serologic responses to each vaccine component. Results: Follow-up was obtained after all 1312 vaccinations . Fever was infrequent in the two treatment groups. Local adverse effe cts of the PRP-T vaccine were infrequent and mild (e.g., redness was n oted in 5.9% of cases and the area of redness was more than 2.5 cm in diameter in 0.8%). The incidence rate of local effects of the DPT-cont aining vaccines was the same in the two groups except for tenderness, which was more frequent in the group given the mixed vaccine (26.6% v. 17.9%, p < 0.001). Serologic data were available for 97% of the subje cts. After the three doses 98.1% of the subjects had a PRP antibody le vel of 0.15 mug/mL or more, and 87.9% had a level of 1.0 mug/mL or mor e, both levels compatible with protection against Hib. Responses to PR P-T were comparable between the treatment groups as were responses to the diphtheria and tetanus toxoids. Pertussis agglutinin titres were r educed after administration of one of two PRP-T lots mixed with DPT va ccine, but responses to four other pertussis antigens were not impaire d. Conclusion: PRP-T vaccine is well tolerated and immunogenic. Combin ed PRP-T and DPT vaccines performed satisfactorily and may be the pref erred method of administration.