The second dose of the hepatitis B vaccine can be given a few days later, but no later than 30 days. Hepatitis B vaccine stimulates the body’s immune system to produce protective antibodies, and the second dose is usually given one month after the first. If you are unable to complete the vaccination on time for personal reasons, it is possible to delay it, but not for more than 30 days. Delaying it too long may affect the response to the vaccine, resulting in the vaccine not working as expected. After the second dose of hepatitis B vaccine is delayed, the third dose of hepatitis B vaccine should also be delayed accordingly. The third dose of hepatitis B vaccine is administered five months after the second dose of hepatitis B vaccine, and one month after the completion of all vaccinations, blood can be drawn to check for hepatitis B surface antibodies to assess the effectiveness of the vaccine.