Blood sampling for Hepatitis B antibody in three-month-old babies is usually chosen from the scalp vein or elbow joint vein. Under normal circumstances, newborns need to be vaccinated against hepatitis B within 24 hours of birth, and after the first vaccination, the second and third vaccination will be given at intervals of one month and six months respectively, according to the procedure of 0, 1, 6. Generally, it is recommended to have a checkup one month after the completion of all three vaccinations to see if any antibodies have been formed. Blood is collected from a vein in the scalp, so that venous blood can be taken for testing, or from a vein on the surface of the elbow or knee joint. If a three-month-old baby has blood drawn to check for hepatitis B antibodies, he or she may not have produced enough antibodies at this time, so it is recommended that a quantitative test be performed and a test order be issued by the pediatrician at a regular hospital.