From 1982-1998, enhanced sentinel surveillance for acute hepatitis B was conducted in 4 counties in the United States to determine trends in disease incidence and risk factors for infection. During this period, the reported incidence of acute hepatitis B declined by 76.1% from 13.8 cases per 100,000 in 1987 to 3.3 cases per 100,000 in 1998. Cases associated with injection drug use (IDU) decreased by 90.6%, men who have sex with men (MSM) by 63.5%, and heterosexual activity by 50.7%. During 1994-1998, the most commonly reported risk factor for infection was high-risk heterosexual activity (39.8%) followed by MSM activity (14.6%) and IDU (13.8%). Over half of all patients (55.5%) reported treatment for a sexually transmitted disease (STD) or incarceration in a prison or jail prior to their illness, suggesting that more than half of the acute hepatitis B cases might have been prevented through routine hepatitis B immunization in STD clinics and correctional health care programs.

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.

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