Transmission route and genotype of chronic hepatitis B virus infection in children in Japan between 1976 and 2010: A retrospective, multicenter study

AimThe aim of this study was to clarify the trends of the infectious source of chronic hepatitis B virus (HBV) infection and the HBV genotype in the Japanese pediatric population over the last three decades. MethodsThe present study was a retrospective, nationwide, multicenter study. Patients who were under 20 years of age when diagnosed with chronic HBV infection were eligible for enrollment in this study. A total of 430 patients (male/female, 256/174; age at the time of writing, 1-37 years; median age, 14 years; birth year, 1976-2010) from 11 hospitals were evaluated. ResultsThe incidence of chronic HBV infection from 1976 to 1980, 1981-1985, 1986-1990, 1991-1995, 1996-2000, 2001-2005 and 2006-2010 was 56, 52, 34, 37, 81, 92 and 78, respectively. Of the 430 patients, 304 (71%), 61 (14%), 11 (3%) and 54 (13%) were infected via mother-to-child transmission, close contact, blood transfusion and unknown source, respectively. After the introduction of perinatal immunoprophylaxis, the rate of mother-to-child transmission increased from 62% during the 1991-1995 period to 86% during the 2006-2010 period. The distributions of genotypes A, B, C, D and F were 3%, 9%, 86%, 2% and 1%, respectively. No obvious change was observed in the distribution of genotypes. Genotype C was significantly associated with mother-to-child transmission. ConclusionMother-to-child transmission remains the primary source of chronic HBV infection after the introduction of immunoprophylaxis. Taking measures to prevent immunoprophylaxis failure is essential to reduce pediatric chronic HBV infection in Japan.