Response of human immunodeficiency virus-exposed and -infected infants to Haemophilus influenzae type b conjugate vaccine.

OBJECTIVE: To evaluate the response of human immunodeficiency virus (HIV)-infected and -exposed infants to the primary series and booster dose of Haemophilus influenzae type b (Hib) conjugate vaccine.
DESIGN: Retrospective study. PATIENTS AND
SETTING: The HIV-exposed and -infected infants who were attending the Special Immunology Family Clinic at The Children's Hospital of Philadelphia (Pa). MAIN OUTCOME MEASURES: Geometric mean antibody titers (GMTs) to Hib polyribosyl ribitol phosphate capsular antigen were assessed after the primary series and again after the 15-month booster doses. In addition, the percentages of patients who responded with polyribosyl ribitol phosphate antibody levels greater than both 0.15 and 1.0 mg/L were compared between groups.
RESULTS: After the 3-dose primary series, the GMTs were lower in the HIV-infected infants compared with those in the HIV-exposed, uninfected infants (0.86 vs 2.30, P = .02). Forty-six percent of the HIV-infected infants mounted a response ( > 1.0 mg/L) compared with that in 79% of the HIV-exposed infants (P = .05). Among the HIV-infected infants, there was no difference in the GMTs based on CD4+ cell counts or HIV-related symptoms. After the 15-month booster dose, the GMTs were not significantly different in the HIV-infected and -exposed infants. As a group, the HIV-infected infants responded to the booster dose with a 2-fold increase in the GMTs, and significantly more of these infants had antibody concentrations above 1.0 mg/L compared with their response to the primary 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 significantly lower than those in the uninfected infants. The primary series of Hib conjugate vaccine appeared to be capable of inducing specific immunologic memory in the HIV-infected infants. The HIV-infected infants had a significant response to a booster dose of Hib conjugate vaccine, as measured by using the GMTs and the percentage of infants with antibody concentrations greater than 1.0 mg/L. The duration of protective titers will need to be followed in this population of patients who are at a high risk for serious bacterial disease.