Vaccines are the suspension of killed or attenuated microbes, or a substance mimicking the disease-causing microbes that are administered into the body to improve the immune system against particular infection. They make the body produce antibodies. These antibodies remain in the blood for long duration. When the disease-causing germs enter the body for second time, these antibodies destroy them.
Hepatitis B is a viral disease caused by infection with hepatitis B virus. So, hepatitis B vaccine also contain the weakened or killed form of hepatitis B virus. Hepatitis B vaccine contain the viral envelope protein ( as antigen) of hepatitis B virus