Changing pattern of age-specific prevalence of hepatitis B surface antigen and corresponding antibody in Japan.

During the period 1978-1984 in Japan, the prevalence of hepatitis B surface antigen (HBsAg) in age groups below age 15 years was 18/2,550 (0.7%), and it was particularly low in the group below age 5 years (2/706 (0.3%)). The low prevalence of HBsAg in children under 15 years of age contrasted sharply with the much higher prevalence in persons age 15 years and older (36/2,050 (1.8%)). In accord with this, the prevalence of antibody to hepatitis B surface antigen (anti-HBs) was much lower in children below age 15 years than that in persons 15 years of age and older (29/2,550 (1.1%) vs. 242/2,050 (11.8%)). Furthermore, the prevalence of hepatitis B viral markers in 1978-1984 was lower than that during the period from 1972-1977 in every age group. A total of 13 (81%) of 16 mothers of carrier children, identified in 1978-1984, were positive both for HBsAg and hepatitis B e antigen in their sera. Now that mother-to-baby transmission appears to be the main route for establishing the persistent carrier state, its interruption should reduce the reservoir of hepatitis B virus, toward its eventual eradication, in Japan.