Incidence of hepatitis A in the United States in the era of vaccination.

CONTEXT

In the United States, hepatitis A is a frequently reported vaccine-preventable disease. Vaccination has been recommended for persons at increased risk since 1996. In 1999, it was recommended that children living in 11 states with the highest incidence of hepatitis A be routinely vaccinated, and that children living in 6 additional states, with incidence above the national average, be considered for routine vaccination.

OBJECTIVE

To assess impact of the current vaccination strategy by evaluating trends in reported cases of hepatitis A since implementation. DESIGN, SETTING, AND CASES: A longitudinal analysis of characteristics of cases of hepatitis A reported in the United States since 1990 to the National Notifiable Diseases Surveillance System.

MAIN OUTCOME MEASURE

Incidence rates of reported cases of hepatitis A. Incidence rates in 2003 were compared with those for the prevaccination baseline period (1990-1997) overall and in the 17 states in which children should be routinely vaccinated or considered for routine vaccination (vaccinating states). Incidence rates in vaccinating states were also compared with those in the remaining states where there is no recommendation for statewide vaccination of children (nonvaccinating states).

RESULTS

Between the baseline period (1990-1997) and 2003, overall hepatitis A rates declined 76% to 2.6 per 100,000, significantly lower than previous nadirs in 1983 (9.2/100,000) and 1992 (9.1/ 100,000). The rate in vaccinating states declined 88% to 2.5 per 100,000 compared with 53% elsewhere (to 2.7/100 000). In 2003, cases from vaccinating states accounted for 33% of the national total vs 65% during the baseline period. Declines were greater among children aged 2 to 18 years (87%) than among persons older than age 18 years (69%); the proportion of cases in children dropped from 35% to 19%. Since 2001, rates in adults have been higher than among children, with the highest rates now among men aged 25 through 39 years.

CONCLUSIONS

Following implementation of routine hepatitis A vaccination of children, hepatitis A rates have declined to historic lows, accompanied by substantial changes in the epidemiologic profile. Greater decreases in the age groups and regions where routine vaccination of children is recommended likely reflect the results of implementation of this novel vaccination strategy. Continued monitoring is needed to verify that implementation continues to proceed and that low rates are sustained.