Interannual variation of the incidence of Haemophilus influenzae type b meningitis.
We conducted a population-based retrospective cohort study to define the annual age-specific incidence of Haemophilus influenzae type b meningitis for birth to 5-year-old residents of King County, Washington, from January 1977 through December 1986. We found naturally occurring wide interannual variations in incidence. The standard deviations of the age-specific incidence during the eight years before the introduction of H influenzae vaccine varied from 26% to 115% of the mean. If short-term changes in incidence were used to assess the efficacy of an H influenzae vaccine (which is less than 100% efficacious and not administered to all susceptible children), the conclusions could be erroneous. To avoid this bias, long-term cohort studies, case/control studies using concurrent controls, or large clinical trials are better choices. We found no significant change in overall incidence during the ten-year study period.
Sherry
B
B
Children's Hospital and Medical Center, Seattle, Wash.
Emanuel
I
I
Kronmal
R A
RA
Smith
A L
AL
Char
L F
LF
Gale
J L
JL
Walkley
E
E
D000367:Age Factors; D016667:Bacterial Capsules; D001428:Bacterial Vaccines; D002675:Child, Preschool; D015331:Cohort Studies; D005260:Female; D018073:Haemophilus Vaccines; D006193:Haemophilus influenzae; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008583:Meningitis, Haemophilus / Q000453:epidemiology* / Q000401:mortality; D011135:Polysaccharides, Bacterial; D012189:Retrospective Studies; D012737:Sex Factors; D013997:Time Factors; D014861:Washington
D001428:Bacterial Vaccines; D018073:Haemophilus Vaccines; C044237:Haemophilus influenzae type b polysaccharide vaccine; D011135:Polysaccharides, Bacterial