The diverse patterns of hepatitis A epidemiology in the United States-implications for vaccination strategies.

Hepatitis A is the most frequently reported vaccine-preventable disease in the United States. Hepatitis A incidence and risk factors during 1983-1995 were examined among cases reported to the study's Sentinel Counties: Denver County, Colorado; Pierce County, Washington; Jefferson County, Alabama; and Pinellas County, Florida. Of 4897 serologically confirmed cases, 611 patients (13%) were hospitalized and 9 (0.2%) died. The average incidence was 14.7/100, 000 (range, 0.6-100.7/100,000, depending on county and year). The frequency of reported sources of infection varied by county, but the largest single group overall (52%) did not report a source. During 3-year communitywide outbreaks in Denver (1991-1993) and Pierce (1987-1989) Counties, rates increased 4- and 13-fold, respectively, and increased in all age, racial/ethnic, and risk groups. During communitywide outbreaks, hepatitis A is not limited to specific risk groups; sustained nationwide reductions in incidence are more likely to result from routine childhood vaccination than from targeted vaccination of high-risk groups.