title: Transmission route and genotype of chronic hepatitis B virus infection in children in Japan between 1976 and 2010: A retrospective, multicenter study.
abstract: OBJECTIVE
  The 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.
  
  
  METHODS
  The 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.
  
  
  RESULTS
  The 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.
  
  
  CONCLUSIONS
  Mother-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.
authors: Department of Pediatrics, Toho University Sakura Medical Center, Sakura, Japan.|Department of Pediatric Hepatology and Gastroenterology, Saiseikai Yokohama City Tobu Hospital, Yokohama, Japan.
authors: Haruki
authors: H
authors: Komatsu
authors: Department of Pediatrics, Toho University Sakura Medical Center, Sakura, Japan.
authors: Ayano
authors: A
authors: Inui
authors: Department of Pediatrics, Toho University Sakura Medical Center, Sakura, Japan.
authors: Tomoo
authors: T
authors: Fujisawa
authors: Department of Pediatrics, Osaka General Medical Center, Osaka, Japan.
authors: Tomoko
authors: T
authors: Takano
authors: Department of Pediatrics, Osaka General Medical Center, Osaka, Japan.
authors: Hitoshi
authors: H
authors: Tajiri
authors: Division of Pediatrics and Perinatology, Faculty of Medicine, Tottori University, Tottori, Japan.
authors: Jun
authors: J
authors: Murakami
authors: Department of Pediatrics, Juntendo University School of Medicine, Tokyo, Japan.
authors: Mitsuyoshi
authors: M
authors: Suzuki
keywords: genotype; hepatitis B immunoglobulin; immunoprophylaxis; mother-to-child transmission; vaccine