Genvac B Hepatitis B Vaccine (Adult) contains 20mcg of purified Hepatitis B surface antigen in a 1ml dose. This vaccine is used to provide protection against the Hepatitis B virus, which can cause liver infection, cirrhosis, and liver cancer. The vaccine is administered as a single dose and is recommended for adults, especially those at risk of exposure to the Hepatitis B virus. It works by stimulating the immune system to produce antibodies against Hepatitis B, offering long-term protection against the infection.