If you have been vaccinated against hepatitis B when you are small, you will get hepatitis B surface antibody, but hepatitis B surface antibody cannot be guaranteed to be present for life, so you can repeat the hepatitis B two-pair test when you grow up to observe the titer of hepatitis B surface antibody, if the titer of hepatitis B surface antibody is higher than 10mIU/mL, you don’t need to get hepatitis B vaccine again, if the titer of hepatitis B surface antibody is lower than If the titer of hepatitis B surface antibody is lower than 10 mIU/mL, you can get another booster of hepatitis B vaccine to increase the titer of hepatitis B surface antibody. Hepatitis B vaccination results in the acquisition of hepatitis B surface antibodies, but the duration is uncertain and is generally thought to last for about 12 years. Hepatitis B surface antibody is a protective antibody. The higher the titer of Hepatitis B surface antibody, the better the protection, and it is generally believed that Hepatitis B surface antibody is most protective when the titer is above 100 mIU/mL.