KEYWORDS:
Hepatitis A, vaccine

BACKGROUND:
Hepatitis A is a vaccine-preventable disease. The hepatitis A vaccine (HAV) was introduced in 1995 and added to the Vaccine for Children program (VFC) in late 1999.

OBJECTIVE:
Assess the relationship between HAV distribution and hepatitis A incidence.

METHOD:
Hepatitis A cases reported to the Los Angeles County (LAC) health department were analyzed; age- and race-specific rates were assessed for the years around the introduction of HAV to VFC (1998 to 2001). Vaccine usage data for public and non-profit clinics were also analyzed.

RESULT:
The number of acute hepatitis A cases has decreased from 1998 to 2001. This decrease is largely due to the decrease in cases reported in Hispanic children, aged 1-14. From 1998 to 2001, hepatitis A incidence (per 100,000) in Hispanics aged 1-4 decreased from 19 to 8, and decreased from 35 to 11 in Hispanic children aged 5-14. Since VFC began offering HAV, vaccine distribution has increased 38% from 139,000 doses in 2000 to 192,000 doses in 2001. According to preliminary data, the use of HAV in public and non-profit clinics increased 18% in children under age 5 from 27,000 doses to 32,000 doses from 2000 to 2001. HAV usage in children aged 5-14 increased from 67,000 doses to 69,000 doses from 2000 to 2001. LAC public and non-profit clinics serve a predominately Hispanic population (41% to 97%). The largest proportion of the LAC clinic clientele are the 1 to 14-year olds.

CONCLUSION:
The introduction of HAV appears to be contributing to significant reductions in reported hepatitis A in LAC, particularly in Hispanic children. Additional studies are needed to confirm the link between vaccine usage with the decrease of disease in Hispanic children.

LEARNING OBJECTIVES:
Alternative methods for linking ecological data to assess relationships between vaccine usage and disease incidence should be further explored.