title: Declining incidence of Haemophilus influenzae type b disease since introduction of vaccination.
abstract: OBJECTIVE
  To determine the incidence of invasive Haemophilus influenzae type b disease in children living in Minnesota and Dallas County, Texas, before and since introduction of plain polysaccharide vaccine in 1985, and conjugate vaccine in 1988. Initially, use of these vaccines was limited to infants 18 months of age and older.
  
  
  METHODS
  Identification of culture-proven cases of H influenzae type b disease was through systems of active, laboratory-based surveillance. The mean incidence of disease (cases observed/100,000 child-years) for 1983 and 1984 served as a baseline for comparison with subsequent years through 1991.
  
  
  METHODS
  Children less than 5 years of age in Minnesota and Dallas County, Texas. Overall, there were 2557 confirmed age-eligible cases of invasive H influenzae type b disease from 1983 through 1991.
  
  
  RESULTS
  Between the 1983-1984 baseline and 1991, the incidence of H influenzae type b disease decreased 85% in Minnesota and 92% in Dallas. Notably, declines in incidence were observed in children in the age group being vaccinated as well as in infants younger than 18 months of age prior to introduction of vaccination.
  
  
  CONCLUSIONS
  In two widely separated areas of the United States, a profound decrease in the incidence of H influenzae type b disease has occurred. The data suggest that vaccination may be protecting against disease, as well as decreasing the spread of infection to unvaccinated infants.
authors.affiliation: Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas 75235-9063.
authors.forename: T V
authors.initials: TV
authors.lastname: Murphy
authors.forename: K E
authors.initials: KE
authors.lastname: White
authors.forename: P
authors.initials: P
authors.lastname: Pastor
authors.forename: L
authors.initials: L
authors.lastname: Gabriel
authors.forename: F
authors.initials: F
authors.lastname: Medley
authors.forename: D M
authors.initials: DM
authors.lastname: Granoff
authors.forename: M T
authors.initials: MT
authors.lastname: Osterholm
mesh_terms: D016667:Bacterial Capsules; D001426:Bacterial Proteins; D001428:Bacterial Vaccines; D002675:Child, Preschool; D004168:Diphtheria Toxoid; D006192:Haemophilus Infections / Q000453:epidemiology* / Q000517:prevention & control; D018073:Haemophilus Vaccines; D006193:Haemophilus influenzae / Q000276:immunology*; D006801:Humans; D015994:Incidence; D007223:Infant; D008910:Minnesota / Q000453:epidemiology; D011135:Polysaccharides, Bacterial; D013781:Texas / Q000453:epidemiology; D014611:Vaccination
chemical_list: D001426:Bacterial Proteins; D001428:Bacterial Vaccines; D004168:Diphtheria Toxoid; D018073:Haemophilus Vaccines; C044237:Haemophilus influenzae type b polysaccharide vaccine; C052180:Haemophilus influenzae type b-polysaccharide vaccine-diphtheria toxoid conjugate; D011135:Polysaccharides, Bacterial; C061963:HibTITER protein, Haemophilus influenzae