Hepatitis B vaccination is a reliable method of preventing hepatitis B. However, the immunity it produces is not absolute and permanent, especially when the level of antibodies produced after hepatitis B vaccination gradually decreases over time to less than the protective value. The hepatitis B vaccine contains a component of hepatitis B surface antigen (HBsAg), which, after vaccination, stimulates the immune system to produce protective hepatitis B surface antibodies (anti-HBs), and once the hepatitis B virus is present in the blood, the antibodies remove it and stop the infection, giving the body immunity against hepatitis B. The hepatitis B vaccination requires three doses of vaccine in a 0, 1, and 6 month schedule, i.e., after the first dose of vaccine, the second and third doses of vaccine are given at one and six month intervals. About 30% of people develop antibodies after the first dose of hepatitis B vaccine, about 50% to 70% after the second, and about 90% after the third, remaining at that level for the second year and dropping to about 74% in the third year. The antibody titer will gradually decrease over time, and when the antibody titer is less than 10 international units/mL, the body will lose immunity to hepatitis B and there is a risk of hepatitis B infection. Antibodies produced after hepatitis B vaccination generally last about 12 years, but the duration of antibody maintenance varies from person to person, with a few people losing their antibodies after 1 to 2 years, and some people lasting more than a decade. In conclusion, hepatitis B vaccination is not a lifelong immunization. For those whose titer of hepatitis B surface antibody is less than or equal to 10 IU/ml, they should be re-vaccinated within six months, and those whose antibody titer is greater than 10 IU/ml can be re-vaccinated within six years, and some experts recommend a booster within three years after immunization. Only when the effective anti-HBs titer is maintained in the body for a long time can hepatitis B virus infection be effectively prevented and the purpose of hepatitis B prevention be truly achieved. Therefore, hepatitis B vaccination can effectively prevent hepatitis B virus infection, but the level of antibodies produced will gradually decline or disappear over time. The protective effect of hepatitis B vaccination is not lifelong, and when the titer of hepatitis B surface antibody is less than the protective value, it should be replenished in time.