After several years of hepatitis B vaccination, the value of hepatitis B surface antibody may decrease or even disappear, because there is a possibility of close contact with hepatitis B patients in daily life, so the hepatitis B surface antibody will neutralize the invading hepatitis B virus and be gradually consumed. No matter how high the antibody value is, every 2 years you should have a repeat examination of the half-two-way test, and when the antibody value is 0mIU/ml, you should have 3 injections of hepatitis B vaccine again. If the surface antibody value is between 0-10mIU/ml, 2 doses of hepatitis B vaccine can be injected; when the antibody value is between 10-100mIU/ml, the individual can choose whether to inject or not according to his/her own will, and it is better to make the surface antibody value more than 100mIU/ml.