[Evaluation of long-term efficacy on plasma-derived hepatitis B vaccine].

From April 1986 to May 1990, 265 pupils aged 5 to 9 years in Xian suburbs were studied to evaluate long-term efficacy of plasma-derived hepatitis B vaccine made in China. Anti-HBs titers in vaccine group reached the highest at twelfth month after the first injection and decreased afterwards. The positive rate of anti-HBs decreased slow, but geometric mean titers of anti-HBs fell sharply. Compared with placebo group, the differences were all significant. The peak anti-HBs titers and the response time positively correlated with the persistence of anti-HBs. 4 years observation showed that protection rate of hepatitis B vaccine against HBV infection was 80%. Protection rate was 100% if HBsAg was only considered.