ANTIBODY-RESPONSE TO UNCONJUGATED HAEMOPHILUS-INFLUENZAE-B AND PNEUMOCOCCAL POLYSACCHARIDE VACCINES IN CHILDREN WITH RECURRENT INFECTIONS

Background: Increasingly, antibody testing is being used to evaluate t he status of humoral immunity in patients with recurrent infection and suspected immunodeficiency. In the past, we had been impressed that i mmunization with unconjugated Haemophilus influenzae b (uHib) vaccine provide useful information about the ability to produce antibody to po lysaccharides and that the use of pneumococcal polysaccharide (PPS) va ccine frequently produced results that were difficult to interpret. Ob jective: The study was carried out to compare antibody responsiveness to vaccination with uHib with the response seen after PPS vaccination. Methods: Twenty children (ages, 2 to 13 years; 11 male) who were refe rred to our immunology clinic because of recurrent infections were imm unized with both uHib vaccine and PPS vaccine. Nine children had previ ously received conjugated Hib vaccine. Results: All 20 children either responded with a twofold or greater increase in antibody titer after uHib vaccine or had preimmunization antibody concentrations of greater than 400 nanograms antibody per milliliter (ng Ab N/ml). All of the c hildren responded to PPS-3 with postimmunization antibody concentratio ns greater than 400 ng Ab N/ml. Three children had an increase in tite r to PPS-7 of less than twofold, seven did not have a twofold increase in titer to PPS-9, and 15 had an increase in titer to PPS-14 of less than twofold. Conclusion: Unconjugated Hib vaccine is a potent immunog en in children over 2 years of age. Prior immunization with the conjug ate vaccine did not prevent a response to unconjugated vaccine. Unconj ugated Hib vaccine appears to be at least as immunogenic as PPS-3 when used as an assessment vaccine of evaluating antibody responsiveness.