Progress Toward Eliminating Hepatitis A Disease in the United States

Hepatitis A virus (HAV) disease disproportionately affects adolescents and young adults, American Indian/Alaska Native and Hispanic racial/ethnic groups, and disadvantaged populations.During 1996During -2006, , the Advisory Committee on Immunization Practices (ACIP) made incremental changes in hepatitis A (HepA) vaccination recommendations to increase coverage for children and persons at high risk for HAV infection. This report examines the temporal association of ACIP-recommended HepA vaccination and disparities (on the absolute scale) in cases of HAV disease and on seroprevalence of HAV-related protection (measured as antibody to HAV [anti-HAV]). ACIP-recommended childhood HepA vaccination in the UnitedStates has eliminated most absolute disparities in HAV disease by age, race/ethnicity, and geographic area with relatively modest ≥1-dose and ≥2-dose vaccine coverage.However, the increasing proportion of cases of HAV disease among adults with identified and unidentified sources of exposure underscores the importance of considering new strategies for preventing HAV infection among U.S. adults.For continued progress to be made toward elimination of HAV disease in the United States, additional strategies are needed to prevent HAV infection among an emerging population of susceptible adults.Notably, HAV infection remains endemic in much of the world, contributing to U.S. cases through international travel and the global food economy.MMWR / February 12, 2016 / Vol.65 / No. 1 US Department of Health and Human Services/Centers for Disease Control and PreventionThe epidemiology of acute HAV disease varies worldwide and is in transition in many areas (8-12).In regions where HAV infection has been considered endemic (e.g., Africa, Asia, Central and South America, and Eastern Europe), up to 90% of children are infected by age 10 years (13).Because asymptomatic HAV infection in endemic settings is almost universal during childhood, and is associated with life-long immunity in these settings, illness and deaths from HAV infection are uncommon at any age.As sanitation, access to clean water, and living conditions improve, a decrease occurs in the proportion of persons protected by infection in childhood, HAV disease becomes more frequent among adolescents and adults, and cycles of outbreaks occur as the proportion of the population that is susceptible increases.Because improvements in conditions that foster transmission occur unevenly across communities, disparities in disease incidence can be accentuated by the quality of living conditions, geography, and race/ethnicity of affected populations (3,9,13).In the United States, transition from intermediate to low endemic HAV infection occurred during the second half of the 20th century.During this period, temporal increases in HAV infection and communitywide outbreaks led to cyclic increases in HAV disease approximately every 10-15 years (Figure 1) (5,11,14).Between cyclic increases, the number of reported cases remained ≥21,000 annually (5).When underdiagnosis and underreporting are accounted for, the actual number of cases was estimated to be two to ten times higher (5,15).In 1994, what appeared to be a new cycle of increasing HAV infection began, with 26,796 reported cases (rate: 10.3 cases per 100,000 population) (5).During 1983-1997, the highest case rates were among children aged ≥5 years and young adults, and the lowest case rates were among adults aged ≥40 years.This pattern was still present in 2000 (Figure 2) (3,5,6,14).The 1988-1994 National Health and Nutrition Examination Survey (NHANES) estimated that approximately one third (37.4%; 95% confidence interval [CI]: 35.1%-39.8%) of U.S. adults aged ≥20 years had antibody to HAV (anti-HAV), presumably from past infection.Among the three major racial and ethnic populations evaluated by NHANES, the highest seroprevalence of anti-HAV was among Mexican-American (81.9%; 95% CI: 79.3%-84.4%)and non-Hispanic black adults (50.0%; 95% CI: 47.8%-52.2%);the lowest prevalence was among non-Hispanic white adults (29.0%; 95% CI: 26.9%-31.1%)(17).Cases were unevenly distributed geographically across the United States.During 1987-1997, the highest case rates were in Alaska and the western states (18) (Figure 3).HAV disease also affected racial/ethnic minority populations disproportionately.Rates were well above the national average of 10.3 cases per 100,000 population among American