Hepatitis A Virus : Secular Trends in the United States
Hepatitis A became nationally reportable as a distinct entity in 1966.
During the prevaccine era in the United States, hepatitis A occurred in
large nationwide epidemics.The largest number of cases reported in one year
was in 1971 (59,606) and the last increase in cases occurred from 1994 to
1995. Prior to 2000, the incidence of reported hepatitis A was
substantially higher in the western United States than in other parts of
the country. From 1987 to 1997, 11 mostly western states (Arizona, Alaska,
Oregon, New Mexico, Utah, Washington, Oklahoma, South Dakota, Idaho,
Nevada, California) accounted for 50% of all reported cases but only 22% of
the U.S. population. Historically, children 2 through 18 years of age have
had the highest rates of hepatitis A (15 to 20 cases per 100,000 population
in the early to mid-1990s).
In 1996, CDC’s Advisory Committee on Immunization Practices (ACIP) recommended administration of hepatitis A vaccine to persons at increased risk for the disease, including international travelers, men who have sex with men, non-injection and injection-drug users, and children living in communities with high rates of disease. In 1999, ACIP also recommended routine vaccination for children living in 11 Western states with average hepatitis A rates of >20 cases per 100,000 population and recommended that vaccination be considered for children in an additional six states with rates of 10–20 cases per 100,000 population. ACIP expanded these recommendations in 2006 to include routine vaccination of children in all 50 states.
Hepatitis A rates have been declining since vaccination initiation in 1996, and since 1998 have been at historically low levels.The number of reported acute hepatitis A cases decreased 93.7% overall from 1990 to 2009, and the last increase in cases occurred from 1994 to 1995. Many of the high-incidence states began routine hepatitis A vaccination programs for children in the late 1990s and since 2002, rates have been similar in all parts of the country, ranging from 0.1 case per 100,000 population in Arkansas, Mississippi, and South Dakota to 1.0 case per 100,000 population in Arizona. Since 2002, rates among children have declined and are now similar to other age groups. The wider use of vaccine is largely responsible for the marked decrease in hepatitis A rates in the United States and similar rates of infection throughout the country, and decreased infection rates in children.
Beginning in the late 1990s, national age-specific rates declined more rapidly among children than adults; as a result, in recent years, rates have been similar among all age groups. Historic differences in rates among racial/ethnic populations also have narrowed in the vaccine era.
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 seroprevalence 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 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).
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