Persistence of hepatitis B vaccine immune protection and response to hepatitis B booster immunization.

AIM:To identify the persistence of immune protection of China-made, plasma derived hepatitis B vaccine after infancy immunization and the time table of booster immunization.METHODS:A cross-sectional follow-up study and an experimental study on booster were used for the evaluation of the serological effect 7 years after vaccination and the antibody anamnestic response. Radioimmunoassay was used for the detection of hepatitis B virus markers. RESULTS:The protective anti-HBs positive rates of 1018 children, who were vaccinated according to the regimen of three doses of 10 &mgr;g hepatitis B vaccine in their infancy, declined from 75.0% during the first two years to 48.2% in the 7th year after the first dosage, however, the positive rates for HBsAg and anti-HBc always fluctuated at a low frequency. A total of 144 subjects aged 6 or 7 years, who were negative for both HBsAg and anti-HBc before booster, were selected from 1018 children of the follow-up study, and boosted with 1&mgr;g intradermally or 2&mgr;g hypodermically hepatitis B vaccines. Their anti-HBs GMT and anti-HBs positive rates were 190.6mIU/ml and 89.6% in the first month after booster,significantly higher than 14.7mIU/ml and 54.9% before booster (P < 0.01), and declined back to 25.3mIU/ml and 75.5% in the 12th month; among 65 children with the anti-HBs negative before booster, 40 had a level of anti-HBS< = 100mIU/ml one month after booster, suggesting retention of immune memory in most of them.CONCLUSION:No need for revaccination against hepatitis B in the 7th year after the initial immunization due to better persistence of immune protection of the vaccine and retention of immune memory to hepatitis B virus in the vast majority of the vaccinees.