Bacterial meningitis in childhood at the Children's Hospital of Pittsburgh: 1988-1998

Bacterial meningitis is an important acute infectious disease of childhood that remains a source of substantial morbidity and mortality. The impact of the Haemophilus influenzae type b (HIB) conjugate vaccines on the epidemiology of the other bacterial causes of meningitis in childhood has received little attention. The objective of this study is to report the experience at a tertiary-care children's hospital with the occurrence of bacterial meningitis before and after the licensure of the HIB conjugate vaccine. With use of International Classification of Diseases diagnostic codes for bacterial meningitis, a list of all children admitted to Children's Hospital of Pittsburgh with a primary or secondary diagnosis of meningitis due to H. influenzae, Streptococcus pneumoniae, and Neisseria meningitidis from January 1, 1988, to December 31, 1998, was constructed. Medical records were examined for basic patient demographic information including age, gender, race, bacterial etiology of meningitis, receipt of vaccine for HIB, underlying conditions, and fatalities. Two hundred twenty-one cases of bacterial meningitis caused by H. influenzae, N. meningitidis, and S. pneumoniae were identified. The age of infected children ranged from 1 month to 18 years, with a mean and median age of 38.1 months and 13 months, respectively. Fifty-two percent of the children were female, 83% were Caucasian and 16% were African-American. Before the routine use of HIB conjugate vaccine, HIB was the bacterial species responsible for the greatest proportion of cases (average of 58%/year). The absolute number of cases of bacterial meningitis attributable to HIB declined after 1991 to an average of 2.5 cases/year. The number of cases of meningitis caused by S. pneumoniae and N. meningitidis have remained relatively stable between 1988 and 1998. The case fatality rates for children with meningitis caused by H. influenzae, S. pneumoniae, and N. meningitidis were 0.0%, 9.2%, and 7.5%, respectively. Most cases of meningitis due to HIB occurred in children who had not been immunized. Three children who received the polysaccharide vaccine developed meningitis due to HIB; there were no failures of the conjugate vaccine.