Small children with low hepatitis B antibody do not need to take three injections again, but only need to take a booster injection of hepatitis B vaccine, which can strengthen the antibody and enhance the body’s immunity to the hepatitis B virus. There are three kinds of hepatitis B vaccines in China, usually the antibody will appear after the second injection, and the antibody will be obviously strengthened after the third injection, but it is worth noting that the hepatitis B vaccine does not mean that it is a lifelong protection, because of the different physical qualities of the individual, the antibody in the body to maintain the length of time there are also differences, and even a part of the population will not produce the antibody, and then need to be vaccinated with a booster shot of the hepatitis B vaccine. To determine whether the hepatitis B vaccine produces antibodies in the child’s body, you can directly go to the hospital to check the hepatitis B two half, if the body antibody has a tendency to decrease or does not produce antibodies, then it is recommended to consult the attending physician, timely injection of hepatitis B vaccine booster shot to ensure that the body produces hepatitis B antibodies to prevent infection.