Infection with hepatitis B virus (HBV) is a major global health problem. Worldwide, it is estimated that 2 billion people have been infected previously and 350 million are chronically infected. While acute HBV infection is associated with significant illness, the risk of chronic infection is of great importance since 5-10% of infected adults will not clear the infection after the initial phase of the illness. About 25% of people who do not initially clear the infection will later develop chronic active hepatitis.