Persistence Of Antibody (Ab) To Haemophilus-Influenzae Type-B (Hib) And Response To Prp And Prp-D Booster Immunization In Children Initially Immunized With Either Vaccine At 15 To 24 Months

Children initially imnunized with PRP or PRP-D conjugate vaccines between 15 and 24 months of age were assessed 1 year later for persistence of AB and response to revaccination with PRP, PRP-D, or normal saline (N=111). Pre and post-vaccination sera were obtained and anti-PRP antibodies were assayed by RIA. Adverse reactions were minor and noted in <5% of vaccinees. AB levels a year after initial immunization were significantly higher in subjects immunized with PRP-D(GM 1.12 ug/ml) than with PRP (0.22 ug/ml)(p<.0001). All groups demonstrated an increase in anti-PRP levels after revaccination, although this response was significantly greater in subjects initially immunized with PRP-D, regardless of booster vaccine given. Initial vaccine: