The second dose of hepatitis B vaccine can be administered 28 days after the first dose, but no later than 60 days. Hepatitis B vaccine is given in three doses, and the immunization procedure is 0, 1, 6, i.e., one dose is given on the same day, the second dose is given one month later, and the third dose is given six months later, completing the entire immunization process in six months in total. The first and second doses can be given at an interval of 28 days, and the second and third doses can be given at an interval of more than 3 months, but the second and third doses cannot be given more than 30 days after the expiration date, and it is possible that antibodies cannot be produced after 30 days, and the vaccination must be repeated.