Prevention of perinatal hepatitis B virus transmission by combined passive-active immunoprophylaxis in Iwate, Japan (1981-1992) and epidemiological evidence for its efficacy.

In a model area in Iwate, Japan, with a population of 1.4 million, the immunoprophylaxis of perinatal transmission of hepatitis B virus (HBV) was started in 1981 and covered >60% of all births already in 1986 when it became mandatory by the national program. Babies born to mothers who carried hepatitis B surface antigen (HBsAg) along with hepatitis B e antigen (HBeAg) in serum received hepatitis B immune globulin (HBIG) at birth and 2 months as well as vaccine at 2, 3 and 5 months after birth. In 1985, 39 of 45 (86.7%) babies who received immunoprophylaxis did not develop the HBV carrier state. During 1986-1992, 100286 of 104493 (96.0%) expecting mothers received tests for HBsAg, and it was detected in 1242 (1.2%) of them. Among the mothers carrying HBsAg, 257 (20.7%) were positive for HBeAg and their babies received immunoprophylaxis. Reflecting effects of immunoprophylaxis, the prevalence of HBsAg decreased from 0.75% (78/10437) in the children born during 1978-1980 to 0.23% (46/20812) in those during 1981-1985 (P<0.001), and further to 0.04% (12/32049) in those during 1986-1990 (P<0.001). The prevalence rates of antibody to HBsAg (anti-HBs) were 1.52, 0.79 and 0.85% in the three groups of children (P<0.001 between those during 1978-1980 and the others). The frequency of antibody to HBV core in the children with anti-HBs diminished remarkably from 76.7% (23/30) in those born in 1971 to 9.0% (6/67) in those born in 1990, thereby indicating a marked decrease in resolved infection and increase in acquired immunity to HBV as the results of immunoprophylaxis.