Children’s hepatitis B antibody disappears too fast is likely to be exposed to the hepatitis B virus, or the body’s immune function has been reduced. If it is found that the antibody to hepatitis B is dropping too fast, it is very likely that the child has been exposed to the hepatitis B virus, or the immune function of the body has been reduced, so the only way to detect the amount of antibody is to carry out a quantitative test of hepatitis B penta-analysis. Through normal vaccination with three doses of hepatitis B vaccine, 90% of children can produce hepatitis B surface antibodies. However, the duration of antibody maintenance varies from person to person, so one month after the three injections of Hepatitis B vaccine, it is recommended to take the Hepatitis B Pentathlon Quantitative Test to check the quantification of Hepatitis B Surface Antibody. If the titer of Hepatitis B surface antibody is >10IU/L, it is very protective against Hepatitis B virus infection. Usually 3~5 years you can retest Hepatitis B Penta Quantitative again to check the titer of Hepatitis B Surface Antibody. If the titer is 1~10IU/L, you can get a booster shot of hepatitis B vaccine in this case. If the titer is <1IU/L, it is necessary to continue to receive three shots of hepatitis B vaccine so as to achieve good protection.