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 epidemio logy of the other bacterial causes of meningitis in childhood has received little attention. The objective of this study is to report the experience a t a tertiary-care children's hospital with the occurrence of bacterial meni ngitis before and after the licensure of the HIB conjugate vaccine. With us e of International Classification of Diseases diagnostic codes for bacteria l meningitis, a list of all children admitted to Children's Hospital of Pit tsburgh with a primary or secondary diagnosis of meningitis due to H. influ enzae, 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, bac terial etiology of meningitis, receipt of vaccine for HIB, underlying condi tions, and fatalities. Two hundred twenty-one cases of bacterial meningitis caused by H. influenzae, N. meningitidis, and S. pneumoniae were identifie d. The age of infected children ranged from 1 month to 18 years, with a mea n and median age of 38.1 months and 13 months, respectively. Fifty-two perc ent of the children were female, 83% were Caucasian and 16% were African-Am erican. Before the routine use of HIB conjugate vaccine, HIB was the bacter ial 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 c ases of meningitis caused by S. pneumoniae and N. meningitidis have remaine d relatively stable between 1988 and 1998. The case fatality rates for chil dren with meningitis caused by H. influenzae, S. pneumoniae, and N. meningi tidis 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 polyp saccharide vaccine developed meningitis due to HIB; the re were no failures of the conjugate vaccine.