The difference between two injections of hepatitis B vaccine and three injections is whether hepatitis B antibodies will be produced. The principle of hepatitis B vaccine is to inject the inactivated hepatitis B virus into the human body to cause the human body to produce hepatitis B antibody, which needs to be injected every three months and needs to be injected three times, and some patients may not be able to produce antibody in their bodies after one or two injections, and they need to be vaccinated for the third time, so the difference between two and three injections of hepatitis B vaccine lies in whether or not hepatitis B antibody will be produced. Three injections of hepatitis B vaccine can maximize the guarantee that hepatitis B antibody can be produced in the body, so it is generally necessary to receive three injections of hepatitis B vaccine, and it should be noted that, if hepatitis B antibody is not produced in the body after three injections, it is necessary to receive high-valence hepatitis B immunoglobulin to ensure that the body contains hepatitis B antibody. Patients are advised to go to the hospital for regular checkups, and if there is any abnormality, they should seek medical advice immediately.