Objective To determine anti-HBs immunology in children who were inoculated with HBV vaccine but had negative ELISA result by quantitative anti-HBs test. Methods Micro-particle Enzyme Immunoassay (MEIA)was used to determine quantitatively anti-HBs concentration in serum of 76 children who were inoculated by HBV vaccine and qualitative anti-HBs (-)result. Results In 41 of all specimen , anti-HBs concentration were higher than 10mIU/ml, 22 lower than 10mIU/ml, 13 lower than 2.1mIU/ml. Conclusions Anti-HBs conc...