Babies who have received two doses of hepatitis B vaccine will not be infected with hepatitis B. After hepatitis B vaccination, the body can be stimulated to produce protective antibodies, i.e., the surface antibody appears positive. Generally speaking, the higher the titer of hepatitis B surface antibody is, the stronger the body’s immunity against hepatitis B will be, and the stronger the effect of resisting hepatitis B will be when contacting hepatitis B patients, etc., so as to prevent being infected. After two injections of hepatitis B vaccine, the body will usually produce antibodies, but the titer of antibodies may not be particularly high, so it is recommended to complete the third injection, so that the titer of antibodies will be higher. Generally, two months after the three injections, the surface antibody of hepatitis B will be tested, if the antibody is positive, it indicates that the injection is effective, and the titer of antibody can be seen by quantitative test. There are very few babies who may not produce antibodies or have low antibody titers due to low immunity, and then it is recommended to re-inject or strengthen the injection, so it is recommended that babies need to be re-checked regularly for hepatitis B surface antibody, and re-injection is needed if it is negative.