Immunogenicity of Haemophilus influenzae type b polysaccharide-tetanus protein conjugate vaccine in children with sickle hemoglobinopathy or malignancies, and after systemic Haemophilus influenzae type b infection

To determine the immunogenicity of Haemophilus influenzae type b polysaccharide-tetanus protein conjugate vaccine in specific populations at risk, we administered vaccine to children with sickle cell anemia (n=19; mean age, 18.3 months, malignancies (n=18; mean age, 43.1 months), or a recent history of systemic H. influenzae type b infection (n=17; mean age, 11.9 months). After one dose of polyribosylribitol phosphate-tetanus toxoid conjugate vaccine the geometric mean titers for polyribosylribitol phosphate antibody were 4.8 μg/ml (14/19 >1 μg/ml), 1.4 μg/ml (9/18 >1 μg/ml), and 5.6 μg/ml (15/17 >1 μg/ml) in these three groups, respectively. Children with sickle cell anemia or a recent history of systemic H. influenzae type b infection had polyribosylribitol phosphate antibody levels comparable to those of normal children of similar age after one or two doses of polyribosylribitol phosphate-tetanus toxoid conjugate vaccine. We conclude that this vaccine is immunogenic in children with underlying conditions associated with an increased risk of H. influenzae type b infection.