The hepatitis B vaccine is a series of three-to-four shots given over a period of six months, and with the exception of people with weakened immune systems, the Centers of Disease Control does not recommend booster shots. Receiving an extra shot or repeating the series is not dangerous.
The hepatitis B vaccine causes the body to develop antibodies against the disease. The body stores these antibodies and uses them to fight the disease in the event of future exposure. People with a hepatitis B infection spread the disease through sexual contact, sharing drug injection or personal care tools, and direct blood contact. Infected mothers sometimes pass the disease to their babies through childbirth, according to the CDC.
A person with exposure to the hepatitis B virus requires immediate medical care. By receiving the vaccine and the hepatitis B immune globulin shot within 24 hours of exposure, the CDC indicates his chances of developing hepatitis decrease significantly.
The hepatitis B virus remains alive outside of the human body for up to seven days, according to the CDC. On average, symptoms appear within three months of exposure. In some people, symptoms do not develop for 20 to 30 years after exposure. Up to 25 percent of infected people develop cirrhosis of the liver or liver cancer due to the disease.