AIM:To understand the anti HBs persistence and the long-term preventive efficacy in rural newborns after vaccination with plasma-derived hepatitis B vaccine.METHODS:In the time of expanded program on immunization (EPI), the newborns were vaccinated with 10&mgr;gcenter dot3 doses of hepatitis B vaccine and 762 newborns who were HBsAg negative after primary immunization were selected for cohort observation from 1986 to 1998. Their serum samples were detected qualitatively and quantitatively for hepatitis B infecting markers, including HBsAg, anti-HBs and anti-HBc by SPRIA Kits. The annual HBsAg positive conversion rate was counted by life-table method.RESULTS:(1)The anti-HBs positive rate was 94.44% for the babies born to HBsAg negative mothers and 84.21% for those born to HBsAg positive mothers in the 1st year after immunization, and dropped to 51.31% and 52.50% in the 12th year respectively.GMT value was dropped from 31.62 to 3.13 and 23.99 to 3.65 in the 2nd to the 12th year respectively. There was a marked drop in GMT at the 3rd to the 5th year, and in anti HBs positive rate at the 9th to the 10th year. (2) In the period of 12 years observation, the person-year HBsAg positive conversion rates were 0.12% (5/4150.0) in newborns born to HBsAg negative mothers and 0.20% (1/508.0) in those born to HBsAg positive mothers, and none of the HBsAg positive converted children became HBsAg chronic carriers. Compared with the baseline before immunization, the protective rates were 97.19% and 95.32% respectively.CONCLUSION:The protective efficacy of plasma-derived hepatitis B vaccine persisted at least 12 years, and a booster dose seems not necessary within at least 12 years after the primary three-doses immunization to newborns born to HBsAg negative mothers.