The third injection of hepatitis B is not recommended to be postponed in principle, and if it is postponed, it is recommended that it should not be postponed for more than one month. Hepatitis B vaccine is recommended to be administered regularly at 0, 1 and 6 months of age, so as to stimulate the body to produce effective hepatitis B antibodies and protect the body from hepatitis B virus infection. If the vaccination is delayed, it may cause the vaccine to be ineffective. However, if it is really impossible to receive the vaccination within the stipulated time for various reasons, it is recommended that the vaccine be replenished within one month. The third injection of hepatitis B vaccine is a booster injection, for infants and young children or adults who do not have the antibody, should be vaccinated regularly according to the regulations, and the hepatitis B vaccine is an effective measure to prevent hepatitis B virus infection.