To determine incidence of invasive Haemophilus influenzae type b (Hib) disease in a defined population of Jeonbuk Province, Korea, children <5 years were evaluated in prospective, population-based surveillance of invasive
bacterial diseases using standardized methods for patient referral, clinical evaluation and laboratory testing (optimized culture,
latex agglutination, polymerase chain reaction).
Vaccine utilization was assessed with vaccination histories of patients in surveillance, monthly data on Hib vaccine distribution and a coverage survey of clinic patients in study population. From September 1999 to December 2001, 2176 children were evaluated for possible
meningitis, 1541 had no cerebrospinal fluid (CSF) findings of
meningitis, 605 had CSF abnormalities (suspected
bacterial meningitis) but no pathogen identified; six patients had probable Hib
meningitis and eight had confirmed Hib
meningitis. The annual suspected
bacterial meningitis incidence was 258.4/100,000 <5 years and the probable/confirmed Hib
meningitis incidence was 6.0/100,000 <5 years.
Pneumococcal meningitis incidence was 2.1/100,000 <5 years and Group B streptococcal
meningitis incidence was 0.17/1000 live births. A total of 69,589 Hib vaccine doses were distributed during the study. Hib vaccine coverage was negligible initially but increased to 16% (complete Hib immunization) and 27% (partial immunization) in final months of study. Suspected
bacterial meningitis incidence was high but proven invasive Hib
meningitis incidence was low. Hib was leading cause of
bacterial meningitis yet bacterial pathogens were identified in only 4% of abnormal CSF. These findings may reflect truly low incidence, presumptive
antibiotic treatment, partial Hib immunization, or incomplete clinical evaluations. Given the apparent Hib
meningitis burden in Jeonbuk Province, additional studies to describe other invasive Hib syndromes, Hib-associated mortality and disability, and economic impact of Hib disease will be useful to guide public health decisions regarding routine Hib vaccine introduction.