Selective antibody deficiency to Haemophilus influenzae type B capsular polysaccharide vaccination in children with recurrent respiratory tract infection.

Fifty-one children between 22 and 158 months of age referred to an immunology clinic with a history of recurrent respiratory tract infections were prospectively evaluated for immunologic abnormalities. Ten of the subjects had a poor response to the Haemophilus influenzae type b (Hib) capsular polysaccharide vaccine (failure to mount a twofold increase in titer or achieve a postimmunization titer greater than 0.2 micrograms ab/ml). There were no differences in mean serum concentrations of IgG, IgM, IgA, isohemagglutinins, or anti-tetanus toxoid between the responders and the nonresponders. None of the 10 nonresponders were deficient in IgG2. Eight of the vaccine failures were immunized with an Hib conjugate vaccine (HbOC) consisting of Hib capsular oligosaccharides coupled to diphtheria toxin. All responded with at least a fivefold increase in antibody after primary immunization with HbOC. Seven of the eight had a postHbOC primary immunization titer greater than 1.0 microgram/ml. This study demonstrates that some children with recurrent infections and with normal IgG subclasses are unable to respond to Hib capsular polysaccharide. This defect, which can be circumvented by presenting the polysaccharide antigen in an alternative form, may be contributing to the symptomatology experienced by these patients.