BACKGROUND:
The Advisory Committee on Immunization Practices (ACIP) recommends that adults with behaviors that put them at high-risk for hepatitis A virus (HAV) infection, including men who have sex with men (MSM) and illegal drug users (IDU), be routinely vaccinated. Correctional facilities, STD clinics, and drug treatment programs serve as potential access points for this population.

OBJECTIVE:
Determine the impact of missed opportunities for hepatitis A vaccination in correctional facilities, STD clinics, and drug treatment programs.

METHOD:
Cases of hepatitis A were identified through sentinel surveillance in six counties during 2001-2004. Cases were defined by acute illness with discrete onset of symptoms and positive test for IgM antibody to HAV. Patients were interviewed to assess risk factors for infection and history of incarceration and STD and drug treatment.

RESULT:
Of 468 cases identified, 416 were in adults (>= 16 years of age) of whom 89% (372) were interviewed. During the 2-6 weeks before onset, 28% of these cases reported IDU, and 23% reported MSM activity; 43% reported either IDU or MSM activity. Of the 159 cases occurring in these groups, 43% (68) had been incarcerated, 33% (53) had visited an STD clinic, and 18% (29) had been in a drug treatment program; 69% (109) had been seen in at least one of these potential vaccination venues.

CONCLUSION:
Over 40% of hepatitis A cases occurred in current IDU or MSM. Over two-thirds of these cases had been seen in settings where HAV vaccine could have been administered. Implementation of hepatitis A vaccine programs in correctional settings, STD clinics, and drug treatment programs might prevent as much as one third of all adult hepatitis A cases.

LEARNING OBJECTIVES:
Understand risk factors for hepatitis A in adults and venues where vaccine could be delivered.