Objective: Haemophilus influenzae type b (Hib) conjugate vaccines were licensed for routine use in the United States in December 1987. We compared national trends in deaths and hospitalization from H influenzae meningitis among children < 5 years old before and after Hib conjugate vaccine licensure.
Methods: H influenzae meningitis mortality rates were calculated using data from the 1980 through 1991 computerized national mortality files. Hospitalization rates from H influenzae meningitis were calculated using data from the 1980 through 1991 National Hospital Discharge Surveys. Trends in H influenzae mortality and hospitalization from 1980 through 1887 were compared with trends from 1988 through 1991. Trends for Streptococcus pneumoniae and Neisseria meningitidis meningitis were also examined.
Results: From 1980 through 1987, mortality from H influenzae meningitis decreased an average of 8.5% each year, compared with a 48% annual decrease from 1988 through 1991 (P < .001 for difference in trends). H influenzae meningitis hospitalization rates increased 1% each year from 1980 through 1987, and decreased an average of 34% each year from 1988 through 1991. There was no significant difference in mortality or hospitalization trends for S pneumoniae or N meningitidis meningitis during the two periods. Among infants, H influenzae meningitis mortality decreased an average of 8% per year from 1980 through 1987 and 43% per year from 1988 through 1991. One- to four-year-old children had similar average annual declines, 8% and 58% for the two periods. Although there were regional differences in the absolute mortality rates, all regions of the country had similar trends in meningitis mortality.
Conclusions: Among US children < 5 years old, we found substantial decreases in deaths and hospitalization from H influenzae meningitis, but not S pneumoniae or N meningitidis meningitis, in the years after Hib conjugate vaccine licensure. These results suggest that the declines in H influenzae meningitis were due primarily to the use of Hib conjugate vaccines.