Objective:To investigate the difference between the sera of the hepatitis B vaccine inoculators and the recovered patients with acute infection in blocking hepatitis B virus infection in vitro. Methods:Titres of anti-HBs were tested by ELISA using Abbott kit in the sera of the vaccinates and the recovered patients with acute hepatitis B virus infection. Hep G2 cells were infected by wild type or “a” determinant mutant of HBV with or without pre-incubation for 1 h by the sera of the vaccinates(group 1) and the recovered patients with acute hepatitis B virus infection(group 2). 24 h later HBV DNA in Hep G2 cells were detected by PCR. The neutralization effect was determined based on the PCR results. Results:There is no significant difference between group 1 and group 2 in blocking wild type of hepatitis B virus infection to Hep G2 at the same concentration in vitro. The sera of group 2 can block the “a” determinant mutant strain HBV infection to Hep G2 cells, but the neutralization effect was weaker than that on wild type of HBV infection. The sera of group 2 have no neutralization effect on the “a” determinant mutant strain HBV infection. Conclusion:The sera of recovered patients with HBV acute infection can block both wild strain and “a” determinant mutant strain of HBV infection, while the sera of hepatitis B vaccine inoculators have no neutralizing effect on “a” determinant mutant strain. It suggested that the new hepatitis B vaccine should include more antigen component such as preS1/S2 to develop neutralization effect on “a” determinant mutant strain HBV, and more component anti-HBV antibodies was very important to protect HBV infected patients from mutant HBV reinfection after liver transplantation.