Serotyping discrepancies in Haemophilus influenzae type b disease--United States, 1998-1999.

Since Haemophilus influenzae type b (Hib) conjugate vaccines were introduced in the United States in 1990, the incidence of Hib invasive disease has declined markedly. The majority of cases of Haemophilus influenzae (Hi) disease are caused by organisms with capsule types other than b or by nontypeable organisms. One of the national health objectives for 2010 is to reduce to zero indigenous Hib invasive disease cases in children aged <5 years (objective 14-1c). In 2000, a total of 297 cases of invasive Hi disease were reported in children aged <5 years; serotype b represented 51 (22%) of 236 cases for which serotype information was known. This report describes inconsistencies in Hib serotyping between state health departments and CDC; these inconsistencies suggest that the burden of Hib disease might be less than estimated previously. Accurate laboratory information is essential for the accurate assessment of progress toward the elimination of Hib in the United States.