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In Reply.—Dr Sullivan raises two important considerations when evaluating vaccines in children, immunogenicity and efficacy, ie, protection against invasive Haemophilus influenzae type b disease. Our data demonstrating an inverse relationship of immunogenicity and Haemophilus influenzae type b capsular polysaccharide—Neisseria meningitidis group B outer membrane protein conjugate vaccine (PRP-NOMP) dosage after a second dose of PRP-NOMP cannot directly address the issue of efficacy. We agree that if we were to assume that children achieving anti-PRP antibody levels greater than 1.0 mg/L were protected against H influenzae type b disease, our finding of anti-PRP geometric mean titers of 7.3 mg/L after the second dose of PRP-NOMP in the 30-μg PRP dosage may not be of clinical significance (as stated in our article) because almost all the children achieved anti-PRP antibody levels greater than 1.0 mg/L. The suggestion that "protection in relation to anti-PRP antibody concentration" can be better assessed by comparing age
WONG VK, KIM KS. Immune Response to Hib Conjugate Vaccine-Reply. Am J Dis Child. 1992;146(2):146-147. doi:10.1001/archpedi.1992.02160140012006