Immunogenicity of Haemophilus influenzae type b capsular polysaccharide and its tetanus toxoid conjugate in patients with recurrent infections or humoral immunodeficiency.

The antibody response to the capsular polysaccharide of Haemophilus influenzae type b was evaluated after vaccination with the capsular polysaccharide or its tetanus toxoid conjugate in 41 randomized patients with recurrent infections, IgA deficiency, common variable immunodeficiency, or the Wiskott-Aldrich syndrome. Serum antibodies were measured using a Farr assay for total antibodies and an enzyme-linked immunosorbent assay for antibodies of the three main immunoglobulin classes and of each IgG subclass. Antibody levels reached concentrations generally considered as protective in the majority of cases, the best response being observed after two injections of the conjugate vaccine with a 1-month interval. Vaccination with the conjugate therefore seems to be promising for the prevention of Haemophilus influenzae type b infections in such patients.