Epidemiological survey of Japanese children infected with hepatitis B and C viruses

Aim: The lack of a nationwide survey on hepatitis B virus (HBV) and hepatitis C virus (HCV) infections in Japan led us to investigate the epidemiological profiles of these infections among Japanese children. Methods: We conducted a questionnaire survey of children (<20 years of age) infected with either HBV (n = 136) or HCV (n = 114), who visited 636 pediatric institutions in Japan from 2003 through 2005. Most HBV‐infected subjects (94%) were born in 1986 or after when a nationwide immunization program for infants born to HBe antigen‐positive carriers was initiated. The transmission routes were divided into five groups: maternal, horizontal (subdivided into intrafamilial, iatrogenic and other horizontal), and unknown transmission. Results: Comparison of subjects born in 1990 or after and those born in 1989 or before, when anti‐HBc and anti‐HCV (c100‐3) screening tests of blood donors began, showed a shift in the relative proportions of maternal, intrafamilial, iatrogenic, other horizontal, and unknown transmission from 52%, 19%, 4%, 7% and 19% to 70%, 14%, 6%, 1% and 9%, respectively, for HBV, which was statistically insignificant (P = 0.120), and from 14%, 0%, 76%, 4% and 7% to 89%, 2%, 4%, 0% and 5%, respectively, for HCV, which was statistically significant (P < 0.001). HBV horizontal transmission did not decrease in proportion. No transfusion‐acquired HCV infection was reported in subjects born in 1993 or after. Conclusion: Maternal transmission is a prominent source of HCV infection among Japanese children. The implementation of measures to prevent HBV horizontal infection is also essential, and the present system of selective vaccination should be expanded to universal vaccination.