If you have hepatitis B antibodies, you will not be infected by the hepatitis B virus again. This is because there are three conditions that must be met for an infectious disease to spread; a source of infection, a certain route of transmission, and the presence of susceptible people. All three conditions must be present at the same time. The so-called susceptible people are those who are not immune to the disease, but if they already have hepatitis B antibodies, they are immune and will not be infected with hepatitis B. In addition, some people, although they have hepatitis B antibodies, will not be infected with hepatitis B virus. In addition, although some people have hepatitis B antibody, but the examination found that the antibody gradually decreases, sometimes even gradually turn negative, this part of the population has a certain risk, if at the same time exposed to a large number of hepatitis B virus, may be infected with hepatitis B virus. It is recommended that this group of people go to the hospital for another hepatitis B vaccination and do a booster to increase the titer of antibody.