Toward elimination of Haemophilus influenzae type B carriage and disease among high-risk American Indian children

Objectives. This report describes the epidemiology of Haemophilus influenza e type b (Hib) invasive disease and oropharyngeal among Navajo and White: M ountain Apache children younger than 7 years in an era of wide-spread immun ization. Methods. We conducted active surveillance for-invasive H influenzae disease from 1992 to 1999 and an oropharyngeal carriage study from 1997 to 1999. T he predominant vaccine used was PedvaxHib. Results. The average annual incidence of invasive Hib disease among childre n younger:than 24 months was 22 cases per 100 000. Of 381 children younger than 7 years, only 1 (0.3%; 95% confidence interval = 0.0%, 1.3%) was colon ized with Hib; 370 (97%) had received 2 or more doses of Hib conjugate vacc ine. Conclusions Among Navajo and White Mountain Apache children, Hib conjugate vaccines have led to a sustained reduction in invasive Hib disease and a re duction in oropharyngeal Hib carriage. The disease incidence among children younger than 24 months remains 20 times higher than in the general US popu lation. Hib elimination will require additional characterization of coloniz ation and disease in these high-risk populations.