Whether the absence of hepatitis B antibody is important depends on whether one is a high-risk group for hepatitis B virus infection, whether one has ever received hepatitis B vaccine, etc. High-risk groups for hepatitis B virus infection include people with hepatitis B in the family, medical personnel, people with repeated blood transfusions, dialysis patients, etc. If you have had the hepatitis B vaccine and had antibodies, and the antibodies have disappeared, and you are not in a high-risk group, it does not matter and you do not need to get a booster vaccine. However, if you have not received the hepatitis B vaccine and are in a high-risk group, it is recommended that you receive the vaccine. Hepatitis B antibodies include surface antibodies, core antibodies and e antibodies. The absence of core and e antibodies is normal and they are not protective antibodies. Surface antibodies are protective antibodies. If you do not have these antibodies, you are not immune to the hepatitis B virus and are susceptible to hepatitis B infection. They can be obtained through hepatitis B vaccination, recessive infection with hepatitis B virus, or by recovering from acute hepatitis B. Chronic hepatitis B can also be acquired if a very small percentage of patients are clinically cured through antiviral therapy. In addition, chronic hepatitis B can also be acquired through autoimmunity with negative HBsAg and clinical cure, but the chances of this are extremely low. People without hepatitis B surface antibodies who have not received the hepatitis B vaccine are advised to get it, and can be checked for surface antibody production 1-2 months after completing the vaccination. After hepatitis B vaccination, people who are not at high risk for hepatitis B virus infection usually do not need booster injections even if their antibody titers gradually decrease or even disappear. This is because after vaccination, there are immune memory cells in the body, which stimulate lymphocytes to produce antibodies when exposed to the hepatitis B virus. However, in the case of people at high risk of hepatitis B virus infection, it is recommended that antibody titers <10IU/ml also require a booster injection to prevent insufficient immune strength.