A PROGRAM TO CONTROL AN OUTBREAK OF HEPATITIS-A IN ALASKA BY USING ANINACTIVATED HEPATITIS-A VACCINE

Objective: To stop an epidemic of hepatitis A in rural Alaska by mass immunization of susceptible persons with 1 dose of an inactivated hepa titis A vaccine.Design: Nonrandomized, uncontrolled trial. Hepatitis A vaccine was offered to all persons in susceptible age groups in villa ges with documented cases of hepatitis A. Immune globulin was not offe red at the time of vaccination. Setting: Twenty-five rural communities located in interior Alaska and along the northwest coast of the Berin g Sea and Arctic Ocean. Participants: Persons without a history of acu te hepatitis A in age groups selected by applying results of a previou s serosurvey conducted on serum collected before the epidemic. Interve ntion: One dose of a formalin-inactivated hepatitis A vaccine was give n to each participant. Adults 20 years of age and older received 1440 enzyme-linked immunosorbent assay units and persons younger than 20 ye ars received 720 enzyme-linked immunosorbent assay units. Prevaccinati on and postvaccination levels of antibody to hepatitis A IgG were obta ined from 136 participants. Main Outcome Measures: An active surveilla nce system was established to detect persons with symptom-atic illness es compatible with hepatitis A; persons who met the illness criteria w ere tested for antibody to hepatitis A IgM. One area (the Kotzebue reg ion), where all communities were offered vaccine, was selected for int ensive surveillance and analysis. Results: During the 12-month period before the vaccine trial, 529 cases of icteric hepatitis A were report ed, and 443 were confirmed to be positive for antibody to hepatitis A IgM. Hepatitis A vaccine was administered to 4930 persons, 3517 of who m were younger than 20 years. After vaccination began, 237 persons pos itive for antibody to hepatitis A IgM were identified during a 60-week surveillance period; 46 were vaccinees and 191 were unvaccinated susc eptible persons. In the Kotzebue region, in communities in which more than 80% of persons considered susceptible were vaccinated, the outbre ak ceased in 4 to 8 weeks, whereas in 1 large community in which less than 50% of susceptible persons were vaccinated, the outbreak continue d for more than 50 weeks. More than 90% of seronegative persons develo ped antibody to hepatitis A IgG 3 to 4 weeks after vaccination. Conclu sion: This trial suggested that by providing both short-term and long- term protection, hepatitis A vaccine used without immune globulin halt ed an established epidemic of hepatitis A in rural Alaska.