Hepatitis B vaccination is the most effective measure to prevent hepatitis B virus infection, but people who have been vaccinated against hepatitis B are not absolutely immune to infection, especially those who do not produce hepatitis B surface antibodies after hepatitis B vaccination. The hepatitis B vaccine contains hepatitis B surface antigen (HbsAg) component, which stimulates the immune system to produce protective hepatitis B surface antibodies (anti-HBs) after hepatitis B vaccination. These antibodies can clear the hepatitis B virus, making a person immune to hepatitis B and not being infected. Three doses of hepatitis B vaccine are required for the entire course. After the first vaccination, the second and third doses are given at intervals of one month and six months. After completing the 3 doses of vaccine, the antibody conversion rate of vaccine recipients is over 90%. A small number of people who have received 3 doses of hepatitis B vaccine do not produce surface antibodies and are at risk of being infected if they come into contact with the hepatitis B virus. The general protection rate after successful hepatitis B vaccination remains above 80% for three years. The duration of antibodies varies from person to person and generally lasts about 12 years, but a few people lose their antibodies after 1 to 2 years and lose resistance to the hepatitis B virus and can be infected with hepatitis B. They need to be vaccinated again with the hepatitis B vaccine to strengthen their immunity. Therefore, people who have had the hepatitis B vaccine may still be infected with hepatitis B. In particular, people who have not produced surface antibodies to hepatitis B after the hepatitis B vaccine, as well as people who have produced surface antibodies but whose antibodies have disappeared, should receive the hepatitis B vaccine again in a timely manner.