The immunogenicity of Haemophilus influenza type b conjugate vaccines in children born to human immunodeficiency virus-infected women

Background. Immunocompromise caused by HIV-1 infection increases the importance of receipt of routine childhood vaccines to prevent infections such as invasive Haemophilus influenzae type B (Hib) disease. The objectives of the study were to evaluate the immunogenicity of Hib conjugate vaccines among HIV-infected children according to clinical and immunologic disease progression as well as viral load. Methods. The concentration of antibody to polyribosylribitol phosphate (PRP) was measured at ~9 and 24 months of age in plasma specimens from children of HIV-infected women enrolled in the Women and Infants Transmission Study. Results. Among 227 children (35 HIV-infected, 192 uninfected) at the 9-month study visit who were known to have received age-appropriate immunization with CRM₁₉₇ mutant Corynebacterium diphtheriae protein-conjugated Hib vaccine, geometric mean antibody concentrations were lower among HIV-infected children (1.64 μg/ml) than among uninfected children (2.70 μg/ml), although the difference was not statistically significant. Anti-PRP antibody concentrations did not vary significantly among these HIV-infected children with predominantly mild- moderate disease progression according to clinical category, immunologic stage or viral load (P ≤ 0.48). The proportion of children with antibody concentrations ≤1.0 μg/ml did not vary significantly according to HIV infection status (73% uninfected, 74% infected) or, if infected, clinical or immunologic disease progression or viral load. Similar results were obtained among 127 children (17 HIV-infected, 110 uninfected) eligible for analysis at the 24-month study visit. Changes in antibody concentrations over time (between 9 and 24 months of age) did not differ significantly among 10 HIV- infected as compared with 72 uninfected children (P = 0.81). Conclusions. These results suggest that HIV-infected children with predominantly mild- moderate disease progression respond reasonably well in terms of a quantitative antibody response to Hib conjugate vaccines during the first 2 years of life. Research to further characterize the immune response to Hib conjugate vaccines and to further delineate the 'durability' of anti-PRP antibody concentrations beyond 2 years of life should be pursued.