Interannual Variation of the Incidence of Haemophilus influenzae Type b Meningitis
- Bettylou Sherry, PhD;
- Irvin Emanuel, MD;
- Richard A. Kronmal, PhD;
- Arnold L. Smith, MD;
- Linda F. Char, RD;
- James L. Gale, MD;
- Edward Walkley, MD
- From The Children's Hospital and Medical Center, Seattle (Drs Sherry and Smith and Ms Char); The Maternal and Child Health Program (Drs Sherry and Emanuel) and the Departments of Epidemiology (Drs Sherry, Emanuel, and Gale) and Biostatistics (Dr Kronmal), University of Washington, Seattle; and Mary Bridge Hospital, Tacoma, Wash (Dr Walkley). Read in part at the 1987 Annual Meeting of the American Public Health Association, New Orleans, Oct 21, 1987.
Abstract
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 <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.
(JAMA. 1989;261:1924-1929)
Footnotes
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Reprint requests to the Maternal and Child Health Program, Department of Epidemiology, SC-36, University of Washington, Seattle, WA 98195 (Dr Sherry).
