Nine-year efficacy of hepatitis B vaccination with low-dose in the third injection

Objective: In order to observe the efficacy of low-dose in the third injection of hepatitis B vaccine. Methods: 126 children aged 5~9 years were enrolled in a double-blind, place-controlled and randomized field trial. They were randomly divided into 10μg and 20μg dose group, and were redivided into 2μg, 5μg, 10μg, 20μg or non-injected subgroups when the third booster injections were given. Results: During the 9 years follow-up, the differences of the anti-HBs levels (GMT) among the groups were not significant at every time (P > 0.05). The GMTs at the ninth year (T₁₀₈) were 7.0, 6.4, 9.9, 6.1, 9.7, 5.4 and 7.4, respectively (P > 0.05). The HBV infection rates among the groups had no significant difference (P > 0.05). The protective rates in the groups were all higher than 75% at T₁₀₈. Conclusion: According to the data, it can be concluded that the third injection with low-dose has no influence on the vaccine efficacy (either short-term or long-term efficacy).