The declining prevalence of hepatitis B virus infection among Asian and Pacific Islander children.

PURPOSE: This article provides a review of the literature on the decline of hepatitis B virus (HBV) infection in Asian and Pacific nations having universal hepatitis B immunization programs. METHODS: Papers on the epidemiology of HBV infection and hepatitis B immunization programs in Asian and Pacific nations were located by searching MEDLINE and libraries for publications in English, and by contacting hepatitis B experts. PRINCIPAL FINDINGS: High endemicity for HBV in Asian and Pacific nations was partly caused by a cycle of high infectiousness, perinatal transmission, and chronic infection from early ages. Higher prevalence of infection has been found in men, some families, communities, and ethnic groups, and in people with high risk behaviors and situations, such as attending day care, getting injections, or sharing personal items. Incidence of acquisition of infection is about 2%-5% per year. Prevalence of HBV infection was declining in some nations before commencing hepatitis B immunization programs, probably because of improvements in medical practices and living conditions. Twenty-seven of 34 Pacific and East and Southeast Asian nations have attained >70% hepatitis B vaccination coverage in infants, and twelve have documented reducing infection or liver cancer to fractions of their former rates. But the immunization programs may be causing natural selection of mutant hepatitis B viruses, necessitating study of the mutants, and modification of serological tests and vaccines. CONCLUSIONS: Practical implications for U.S. health professionals are: increasing HBV screening and hepatitis B vaccination of adolescents and adults from Asian and Pacific nations can prevent many infections and disease cases; most children coming from high coverage Asian and Pacific nations will be immune and few infected; we can learn much from these successful programs; and we should still make efforts to immunize Asian and Pacific children in the United States, and help Asian and Pacific nations which do not yet have highly successful hepatitis B immunization programs.