COMPARISON OF MULTIPLE IMMUNIZATION SCHEDULES FOR HAEMOPHILUS-INFLUENZAE TYPE-B CONJUGATE AND TETANUS TOXOID VACCINES FOLLOWING BONE-MARROWTRANSPLANTATION

Antibody concentrations to vaccine-preventable diseases decline follow ing BMT and an optimal schedule for vaccination after transplant has n ot been established. We examined antibody responses to tetanus toroid (TT) and Haemophilus influenzae type b-conjugate (HIB) vaccines of BMT patients immunized at 6, 12 and 24 months (6 month group, n = 21) and compared them to those previously reported for patients immunized at 3, 6, 12 and 24 months (3 month group, n = 74) or at 12 and 24 months (12 month group, n = 17) following transplantation. Geometric mean tot al anti-HIB and IgG anti-TT concentrations were significantly higher a fter the 12 month dose in the 3 and 6 month immunization groups compar ed to the group who received their first dose at 12 months. Although H IB antibody concentrations were higher in the 3 month and 6 month grou ps 12 to 24 months after BMT, the proportion of patients with protecti ve levels was not significantly different from the proportion protecte d in the 12 month group, Following the 24 month immunizations, geometr ic mean antibody concentrations to HIB and TT were similar for all thr ee immunization groups. The proportion of patients in each group with protective levels of HIB antibody after the 24 month dose was greater than or equal to 80%. A two dose schedule of HIB and TT vaccines at 12 and 24 months after BMT should afford protection.