HBV infection is characterized by loss of appetite, listlessness, jaundice, diarrhea, vomiting, and pain in the muscles, abdomen, and joints. It often leads to severe liver damage, liver cancer, or death. Although there is no cure for hepatitis B, a vaccine has been available since 1982. The vaccine, which uses recombinant-DNA technology to bioengineer yeast cells, contains a nonliving hepatitis B surface antigen known as [HBsAg].