The simple answer to ‘How long does a hepatitis B vaccine last?’ is that the full course of a Hepatitis B vaccine includes three vaccinations that may be enough to last for a life time. The second dose of this series should be given one month after the first one, and third dose should be 6 months after the first one. These vaccines can be given with other vaccines esp. Hepatitis A + B. It is also important to realize that normally protective antibodies induced with hepatitis B vaccine lasts up to 15 years.