HBsAg (also known as the Australia antigen) is the surface antigen of the hepatitis B virus (HBV). It indicates current hepatitis B infection.
It is commonly referred to as the Australia Antigen. This is because it was first isolated by the American research physician and Nobel Prize winner Baruch S. Blumberg in the serum of an Australian Aboriginal person. It was discovered to be part of the virus that caused serum hepatitis by virologist Alfred Prince in 1968.
Heptavax, a “first-generation” hepatitis B vaccine in the 1980s, was made from HBsAg extracted from the blood plasma of hepatitis patients. Current vaccines are made from recombinant HBsAg grown in yeast.