The changing epidemiology of hepatitis A in Arizona following intensive immunization programs (1988-2007)

Abstract Introduction Arizona had the highest hepatitis A incidence of any U.S. state during 1987–1997. In 1995, the first hepatitis A vaccines became available in the U.S. A series of hepatitis A vaccination policies and recommendations were implemented in 1996–2006. Our objective was to examine the shifting epidemiologic patterns in hepatitis A in Arizona from 1988 to 2007. Methods Passive surveillance reports to the Arizona Department of Health Services were used to compare hepatitis A rates by age, race/ethnicity and geographic area, before and after widespread vaccination. Reported risk factors and possible sources of infection were compared for two time periods. Age-adjusted incidence during three periods was mapped. Results Overall hepatitis A incidence in Arizona fell from 58 cases per 100,000 in 1988 to 2 per 100,000 in 2007. The proportion of reported cases among children dropped from 62% in 1994–1995 to 32% in 2006–2007. Racial/ethnic disparities between American Indians and non-Hispanic White populations have been eliminated. The geographic distribution of cases within the state has shifted. Earlier cases were likely to report contact with another hepatitis A case or childcare facilities, while later cases indicated recent international travel. Conclusion A major shift in the overall burden of hepatitis A and hepatitis A transmission has occurred in Arizona since the widespread implementation of immunization policies and the concomitant rise in vaccination rates in the state. Current transmission has shifted to older age groups and disparities by race/ethnicity are now highest in Hispanic populations. Future strategies to further reduce hepatitis A transmission may require broadening recommendations to include general adult populations without previous vaccination history.