Learning Objectives for this Presentation:
By the end of the presentation participants will be able to
1. Understand the current epidemiology of Hi invasive disease in the U.S.
2. Understand the importance of serotype for assessing vaccine program impact.


Background:
Prior to the availability of Haemophilus influenzae serotype b (Hib) conjugate vaccine in the late 1980s, Hib was the leading cause of bacterial meningitis and other serious invasive diseases among children <5 years. Reported cases of Hib in this age group continue at low levels; although incidence rates have remained below 0.3/100,000 since 1996, Healthy People 2010 goals are not being met.

Objectives:
Describe recent epidemiology of Hi invasive disease in children <5 years.

Methods:
Analysis included cases of Hi in children <5 years reported through the National Notifiable Diseases Surveillance System (NNDSS) supplemented by data from the Active Bacterial Core Surveillance and states.

Results:
From 2003-2005, 6402 cases of invasive Hi were reported. Of the total, 1068 (17%) were reported among children <5 years. Only 603 (56%) cases <5 years had serotype results.
Of the 1068 Hi cases <5 years, 36% had primary bacteremia. Average annual incidence of Hi was highest among American Indians/Alaska Natives (10.12/100,000) and lowest among Asians/Pacific Islanders (0.81/100,000). Clinical outcome was known for 209 (66%); 12 (6%) died.
Of the 603 Hi cases <5 years with serotype results, preliminary data show Hib accounted for 76 (13%) cases; average annual incidence was 0.13/100,000. Outcome was known for 55 (72%); no deaths were reported. Of Hib cases, 8 (10%) were younger than 2 months of age, 47 (62%) were 2-15 months, and 21 (28%) were 16-60 months.
The rate of non-type b Hi for children <5 years was 0.87/100,000.


Conclusions:
Hib remained an infrequent cause of invasive disease among children. American Indians/Alaska Natives had the highest rates of Hi disease. Missing serotype information compromises vaccine program assessment.