Whether or not the hepatitis B vaccine needs to be reinjected after birth depends on whether or not the hepatitis B surface antibody is positive and how high or low the antibody value is. Some people do not produce antibodies after receiving the vaccine, so in this case they are not immune to hepatitis B. In order to prevent being infected by the hepatitis B virus, they need to be reinjected with the hepatitis B vaccine. In some cases, although antibodies are produced, the antibody value is very low, less than 10 mIU/ml. After a period of time, the antibodies may turn negative, but the hepatitis B vaccine still needs to be reinjected for booster. Even if the antibody value is high, it is still necessary to review the two pairs of half regularly. If you have close contact with hepatitis B patients in your daily life, the hepatitis B antibody may be consumed slowly, and when the antibody is consumed, the body is still vulnerable to hepatitis B infection.