The changing epidemiology of hepatitis A in children and the considerationof active immunization in Korea

Currently, Korea is a low endemicity country for HAV, especially in childre n. However, recent reports of hepatitis A outbreaks show that there has bee n a shift of disease incidence to adolescents and young adults, with 2 case s of acute liver failure in one reported outbreak. We need to study the imm une status for HAV in order to provide information for the establishment of preventive measures and possible consequences of HAV in Korea. A total of 334 infants, children and adolescents less than 20 years of age living in r ural areas of Kyonggi Province, Korea were evaluated for anti-HAV immune st atus in 1996. Five hundred and eighty-four primary school children living i n the same area were separately evaluated for the natural seroconversion ra te between 1993 and follow-up samples taken in 1996. Anti-HAV IgG antibody was measured by enzyme immunoassay (HAVAB EIA kit, Abbott Laboratories, Chi cago, Illinois, USA). In comparison with previous reports of seroprevalence rates, our data confirmed a dramatic drop in seroprevalence rates among ch ildren and adolescents under 20 years of age living in rural areas, from ov er 63.8% two decades ago to 4.6% in 1996. Natural acquisition of HAV antibo dy in primary school children rarely occurs, registering only 0.5% during t hree years. Several outbreaks in young adults during 1996-1998 suggested th at immunity against HAV in this population is so low that massive outbreaks are unavoidable. Teenagers and young adults, especially soldiers, who are likely to be exposed to contaminated food or water, would also have a great er risk of hepatitis A. immunizing children with HAV vaccine as a routine s chedule should also be considered in Korea in the future, particularly if t he disease burden could be estimated and the cost-effectiveness of the vacc ine could be proved.