Context: The impact of routine hepatitis A vaccination of children living in large communities with elevated disease rates has not been evaluated.
Objective: To determine the effect of routine vaccination of children on disease incidence in a community with recurrent hepatitis A epidemics.
Design, setting, and participants: Community-based demonstration project conducted from January 12, 1995, through December 31, 2000, in Butte County, California, among children aged 2 to 17 years.
Intervention: In 1995, vaccination was offered to children aged 2 to 12 years during vaccination clinics conducted on 2 occasions 6 to 12 months apart at most schools in the county. In 1996-2000, vaccine was distributed to community health care clinicians, who vaccinated eligible children without charge. Vaccine was also available at health department clinics, selected child care centers, and other sites.
Main outcome measures: Hepatitis A vaccination coverage, hepatitis A incidence, and vaccine effectiveness.
Results: During the study period, 29 789 (66.2%) of an estimated 44 982 eligible children received at least 1 vaccine dose; 17 681 (39.3%) received a second dose. The number of hepatitis A cases among the entire county population declined 93.5% during the study period, from 57 cases in 1995 to 4 in 2000, the lowest number of cases reported in the county since hepatitis A surveillance began in 1966. The 2000 incidence rate of 1.9 per 100 000 population was the lowest of any county in the state. Of the 245 cases reported during the 6-year period, 40 (16.3%) occurred among children 17 years of age or younger, of which 16 (40%) occurred in 1995 and only 1 in 2000. One of the 27 case patients eligible for vaccination had been vaccinated, having received the first dose 3 days before symptom onset. The estimated protective vaccine efficacy was 98% (95% confidence interval, 86%-100%).
Conclusions: In this population, hepatitis A vaccine was highly effective in preventing disease among recipients. Childhood vaccination appears to have decreased hepatitis A incidence among children and adults and controlled the disease in a community with recurrent epidemics.