Hepatitis B vaccination 2 is also effective when delayed for 20 days. When hepatitis B vaccination is standardized, hepatitis B 2nd injection needs to be given one month after the 1st injection, and the repeat hepatitis B vaccination is to increase the antibody concentration in the body. Antibody titer will disappear slowly after the 1st injection of hepatitis B vaccine, and the 2nd injection of hepatitis B vaccine within the stipulated time can effectively stimulate the body to produce antibodies, so that the antibodies can reach the effective concentration. It is recommended to receive Hepatitis B vaccine on time. If it is necessary to postpone for 20 days due to special circumstances, it is also possible to take the vaccine, and there is also some effect, because the B lymphocytes in the body have a certain memory function, and the injection of the 2nd injection can also wake up the B lymphocytes in the body to produce antibodies, and the antibody titer may be lower compared with that of taking the 2nd injection on schedule, but there is also an effect.