Should I be re-vaccinated after receiving the hepatitis B vaccine? How long is its immune protection period? This is a question of concern. The 15-year follow-up observation of children vaccinated with hepatitis B vaccine in Longan County, Guangxi shows that the positive rate of hepatitis B surface antigen was 1.9% in the vaccination group, 16.7% in the control group, and the protection rate was 88.6%. 50.9% of the vaccination group were positive for hepatitis B antibody at 15 years, which means that the immunity of hepatitis B vaccine can last up to 15 years. After vaccination with hepatitis B vaccine, although the antibody level of the vaccinees decreases year by year as time lengthens, when they are attacked by the hepatitis B virus, the antibody level can rise again due to the immune memory effect, which is especially evident in the high prevalence areas and high-risk groups of hepatitis B. Therefore, in general, if a person is fully vaccinated against hepatitis B and produces high titers of hepatitis B antibodies after vaccination, the vaccination may not be repeated within 10 years, and after 10 years or more, the hepatitis B virus antibodies should be retested and the antibodies may turn negative or decrease in titers. However, the situation of each vaccinated person may be different, so a specific analysis should be made for each case. For example, a recent national survey on the vaccination rate of hepatitis B vaccine shows that the full vaccination rate in China is only 28.4%, and 73.6% are not fully vaccinated. Children who are not fully vaccinated may have no hepatitis B antibodies or low antibody titers, and such children should be tested for hepatitis B antibodies, and if antibodies are not produced or have disappeared, they should be re-vaccinated in a timely manner. It is worth noting that even after receiving the full course of hepatitis B vaccination, 5% to 10% of vaccinated children do not produce hepatitis B antibodies or produce only low titers of antibodies. For these non-responders or low responders, children should receive multiple doses of hepatitis B vaccine or be revaccinated after booster immunotherapy until antibodies are produced. In addition, children who have a high chance of being infected with hepatitis B virus, such as those whose parents or family members are carriers of hepatitis B virus, should be monitored regularly for antibody levels and indicators of hepatitis B infection, and should be revaccinated as soon as their antibodies drop to low levels or disappear completely.