There are limited data concerning safety and immunogenicity of Haemophilus influenzae type b polysaccharide vaccine in children with sickle cell disease. Ninety-eight patients with sickle cell disease (65 with SS phenotype, 23 with SC phenotype, and 10 with Sβ-thalassemia) 1.5 to 20 years of age were given 25 µg of vaccine subcutaneously. The vaccine was well tolerated; mild side effects were observed in 6 of 98 (6.1%) children. In addition, one patient with a recent vasoocclusive crisis was hospitalized because of fever and vasoocclusive crisis 8 hours after vaccination. Prevaccination anticapsular antibody concentrations (by radioimmunoassay) were <0.15 µg/mL in 7 of 11 children 18 to 24 months of age (geometric mean 0.17 µg/mL), in 10 of 25 children 2 to 5 years of age (geometric mean 0.36 µg/mL), and in 3 of 50 patients 6 to 20 years of age (geometric mean 1.03 µg/ mL). Inadequate response (1-to 2-month postvaccination antibody level <1 µg/mL) was found in 3 of 5 children 18 to 24 months of age (geometric mean 1.74 µg/mL), in 8 of 21 children 2 to 5 years of age (geometric mean 2.20 µg/mL), and in 2 of 49 patients 6 to 20 years of age (geometric mean 18.03 µg/mL). Six months after vaccination, >1 µg/mL of antibody was present in the 2 children 6 to 20 years of age with inadequate response but not in the 7 children 2 to 5 years of age with inadequate response. In the 2- to 5-year group, there was a significant correlation of log postvaccination antibody level with prevaccination antibody level but not with age, sex, disease type, disease severity, serum IgG, IgM, or IgA, or presence or absence of Howell-Jolly bodies on blood smear. In contrast to the response of patients with sickle cell disease older than 5 years of age and of 2- to 5-year-old children without disease, H influenzae type b polysaccharide vaccine is not reliably immunogenic in children younger than 6 years of age with sickle cell disease and cannot be relied upon for protection of this age group from H influenzae type b disease.
Antibody responses to Haemophilus influenzae type b conjugate vaccine in sickle cell disease.