The Hepatitis B vaccine is a recombinant subunit vaccine because it contains only the hepatitis B surface antigen (HBsAg) produced using recombinant DNA technology in yeast cells. This antigen alone is sufficient to stimulate an immune response without using the whole virus. In contrast, BCG is a live attenuated vaccine, Oral polio vaccine is a live attenuated vaccine, and Measles vaccine is also a live attenuated vaccine. The recombinant subunit vaccine design improves safety by eliminating the risk of infection from the vaccine itself.

Reference: Harrison's Principles of Internal Medicine, Kasper et al., 20th Edition.