In 2010, a total of 1,670 cases of acute hepatitis A were reported nationwide to CDC. The overall incidence rate for 2010 was 0.5 cases per 100,000 population. The rate was similar among all age groups and gender. However, beginning in 2008, rates among Asian Pacific Islanders were higher than those among all other racial/ethnic populations. Based on data from the National Health and Nutrition Examination Survey (NHANES) conducted from 1999 through 2006, the overall seroprevalence of total antibody to HAV (anti-HAV) among the general U.S. population was 34.9% and 28.1% among U.S.-born individuals alone. Seroprevalence of HAV antibody increases with age, from 22.9% among 6- to 11-year-olds to 59.7% among persons 60 years of age and older. In this survey, anti-HAV seropreva- lence was highest among Mexican Americans not born in the U.S. regardless of age, and seroprevalence was higher among U.S.-born Mexican Americans compared with U.S-born non- Hispanic white and non-Hispanic black persons for all age groups. Asian Pacific Islanders were not included as a race/ ethnic category in this survey. The 1988 to 1994 NHANES total population age-adjusted seroprevalence of anti-HAV was not significantly different from the 1999-2006 age- adjusted seroprevalence. However, the overall age-adjusted seroprevalence increased among U.S. born children (6-19 years) during 1999-2006 compared to 1988-2004 from 8% to 20.2%. In addition, for individuals younger than 40 years, seroprevalence was higher in vaccinating states compared
Hepatitis A 141 9 to non-vaccinating states for all age groups. This suggests increased hepatitis A vaccination rates following the 1999 ACIP recommendations. The rate of hospitalization for hepatitis A in the United States declined more than 68% from the pre- to post-vaccine era (1996-2004) for all age groups. Similarly the rate of ambulatory care visits declined more than 40%. Medical expenditures for both hospitalizations and ambulatory care visits were estimated to have declined by approximately 68% ($29.1 to $9.3 million). Case Definition The 2012 case definition for hepatitis A was approved by the Council of State and Territorial Epidemiologists (CSTE) and published in a 2011 position statement. The clinical description for acute hepatitis A is an acute illness with a discrete onset of any sign or symptom consistent with acute viral hepatitis (e.g., fever, headache, malaise, anorexia, nausea, vomiting, diarrhea, and abdominal pain), and either a) jaundice, or b) elevated serum alanine aminotransferase (ALT) or aspartate aminotransferase (AST) levels. Since HAV cannot be differentiated from other types of viral hepatitis on clinical or epidemiologic features alone, serologic evidence of HAV-specific antibody is necessary. The diagnosis of acute hepatitis A requires the presence of HAV-specific IgM antibody. Hepatitis A Vaccine Characteristics Two inactivated whole-virus hepatitis A vaccines are available: HAVRIX (GlaxoSmithKline) and VAQTA (Merck).