RESPONSE OF HUMAN-IMMUNODEFICIENCY-VIRUS-EXPOSED AND HUMAN-IMMUNODEFICIENCY-VIRUS-INFECTED INFANTS TO HAEMOPHILUS-INFLUENZAE TYPE-B CONJUGATE VACCINE

Objective: To evaluate the response of human immunodeficiency virus (H IV)-infected and -exposed infants to the primary series and booster do se of Haemophilus influenzae type b (Hib) conjugate vaccine. Design: R etrospective study. Patients and Setting: The HIV-exposed and -infecte d infants who were attending the Special Immunology Family Clinic at T he Children's Hospital of Philadelphia (Pa). Main Outcome Measures: Ge ometric mean antibody titers (GMTs) to Hib polyribosyl ribitol phospha te capsular antigen were assessed after the primary series and again a fter the 15-month booster closes. In addition, the percentages of pati ents who responded with polyribosyl ribitol phosphate antibody levels greater than both 0.15 and 1.0 mg/L were compared between groups. Resu lts: After the 3-dose primary series, the GMTs were lower in the HIV-i nfected infants compared with those in the HIV-exposed, uninfected inf ants (0.86 vs 2.30, P=.02). Forty-six percent of the HIV-infected infa nts mounted a response (>1.0 mg/L) compared with that in 79% of the HI V-exposed infants (P=.05). Among the HIV-infected infants, there was n o difference in the GMTs based on CD4(+) cell counts or HIV-related sy mptoms. After the 15-month booster dose, the GMTs were not significant ly different in the HIV-infected and -exposed infants. As a group, the HIV-infected infants responded to the booster dose with a 2-fold incr ease in the GMTs, and significantly more of these infants had antibody concentrations above 1.0 mg/L compared with their response to the pri mary series (62% vs 38%, P=.02). Conclusions: Most of the HIV-infected infants responded to the primary series of Hib conjugate vaccine with antibody concentrations greater than 0.15 mg/L, but the GMTs were sig nificantly lower than those in the uninfected infants. The primary ser ies of Hib conjugate vaccine appeared to be capable of inducing specif ic immunologic memory in the HIV-infected infants. The HIV-infected in fants had a significant response to a booster dose of Hib conjugate va ccine, as measured by using the GMTs and the percentage of infants wit h antibody concentrations greater than 1.0 mg/L. The duration of prote ctive titers will need to be followed in this population of patients w ho are at a high risk for serious bacterial disease.