[Long-term efficacy of infant hepatitis B immunization program].

Objective: To evaluate the long-term efficacy of infant hepatitis B (HB) immunization program on preventing hepatitis B virus (HBV) infection, and to assess its impact on the incidence of HB in children.

Methods: Since 1986, the universal HB vaccination for newborn babies with standard, pediatric dose had been launched without serologic prescreening of pregnant women for HBsAg, in a high endemic county of Long-An. A hepatitis surveillance system was set up to evaluate the possible impact on the incidence of hepatitis B. To serologically evaluate the effectiveness of the program, a stratified random sampling of 1000 children in 1987 birth cohorts, who received plasma-derived HB vaccine, was recruited for long-term follow up at the age of 1 to 13 years. A cross-sectional seroepidemiological survey was conducted in the county in 1985, before the program, and in 2001, for 1551 children born in 1996-2000 who were administered yeast recombinant HB vaccine.

Results: During the 1 to 13 years after the program, the rates of HBsAg-positive were 0.7% to 2.9% with an average of 1.7% and the protective rates were 83.5% to 96.6%. HBV infection rates were 1.1% tp 5.1% with an average of 2.4% and the protective rates were 93.5% to 98.4%. For the population aged 1 to 4 years who were immunized with recombinant HB vaccine, HBsAg positive rates were 1.8% to 2.4% with an average of 2.0% and the protective rates were 78.4 to 85.2%. 14 years after the program, the cumulative incidence of acute hepatitis B in the children aged 1 to 14 years fell to 1.5 cases per 100,000 children, down 91.8% as compared with that in 1985 to 1987. However, the cumulative incidence of 14.4 cases per 100,000 population in unvaccinated children was not significantly different from that in the history controls. Acute hepatitis B children had not been reported, showing that the vaccination program was 100% protective in children.

Conclusion: The universal infant HB vaccination program in a hyperendemic area has proved to be effective in controlling HBV infection and decreasing the incidence of acute hepatitis B in children. Booster dose is unnecessary in 13 years after the immunization. The protective efficacy of yeast recombinant HB vaccine is similar to that of plasma-derived HB vaccine.