Current Epidemiology and Trends in Invasive Haemophilus influenzae Disease—United States, 1989-2008

Background. With the introduction of Haemophilus influenzae serotype b (Hib) conjugate vaccines, there has been a dramatic reduction of Hib disease in young children and the epidemiological trends of invasive H. influenzae have shifted. Methods. Data were collected from active surveillance for invasive H influenzae disease conducted through Active Bacterial Core surveillance sites during 1989-2008. Results. During 1999-2008, the estimated mean annual incidence of H. influenzae infection was 1.62 cases per 100 000 population; 15.3% of cases were fatal. Incidence was higher among adults aged ≥ 65 years, compared with other age groups. The largest burden of disease among children aged < 5 years was in infants aged < 1 year; many of these cases occurred during the first month of life in preterm or low-birth weight infants. An estimated 10% of the total burden of disease among children aged < 5 years occurred in American Indian and Alaska Native children.During 1989-2008, 7559 cases of H influenzae disease were reported from Active Bacterial Core surveillance sites. Small increases in the incidence of serotypes a, e, and f were observed during 1989-2008. The largest of these increases was in serotype fand was primarily among adults aged ≥18 years. Conclusions. Since the introduction of Hib conjugate vaccines, the incidence of invasive disease caused by H influenzae in the United States has decreased dramatically; however, a considerable burden of non-Hib disease is still present in the oldest and youngest age groups. There is no evidence of substantial replacement disease with non-b serotypes in young children in the United States.