[A study on the effectiveness of hepatitis B vaccine among the vaccinated population].

In order to identify the effect of hepatitis B vaccine in a vaccinated population, 5890 persons from 1890 families in 13 counties/cities in Henan province were chosen for investigation under multistage cluster systematic sampling. All subjects were bled for HBsAg, anti-HBs and anti-HBc by RIA. The positive rate of HBsAg was significantly lower in vaccinates than in that non-vaccinates. There was no protective effect in those who only vaccinated for one dose. It was preferable to receive vaccination before the age of two years. If 70% of hepatitis B vaccine coverage was reached among those younger than 5 years old, the positive rate of HBsAg could reduce to 1% or even lower. Results showed that it was important to ensure an earlier and full course vaccination with high coverage.