Immunogenicity and tolerance of H. influenzae type b, tetanus toxoid conjugate vaccine given concurrently or in combination.

The present prospective, open, controlled, randomised comparative trial was undertaken to evaluate the sero response and side effects of PRP-T Conjugate Vaccine (ACT-HIB) in infants and children aged 2 months and 16-24 months. Fifty four babies aged 2 months formed group A, 56 children aged 16-24 months formed group B. Groups A and B were further subdivided into two sub groups each destined to receive either PRP-T vaccine in association with DPT vaccine at different sites (I) or PRP-T and DPT both vaccines at the same site mixed in the same syringe (II). Group A received 3 doses at 2, 3 and 4 months of age and group B received one dose between 16-24 months. The Geometric mean titres of Anti PRP antibodies observed in primary immunisation schedule (A) and single dose vaccination schedule (B) were comparable and significantly higher to prevaccination titres. A serum anti PRP level of > 1.0 mcg/ml after immunisation is believed to correlate with long term protection. Ninety-six percent of infants in Group A and 98% in Group B achieved titres > 1.0 mcg/ml. The side effects were minimal, local and were comparable between the study and control groups, suggesting that PRP-T vaccine is highly immunogenic and well tolerated in Indian infants and children.