Type B hepatitis: a review of current prospects for a safe and effective vaccine.

Several subunit vaccines against hepatitis B virus (HBV) have been developed and either are being evaluated or soon will be evaluated for their ability to prevent HBV infection in humans. Most of these preparations consist of highly purified, 22-nm spherical particles of hepatitis B surface antigen (HBsAg) that have been extracted from the plasma of chronic carriers of HBV and inactivated with formalin. Extensive testing in humans and chimpanzees showed these vaccines to be free of residual HBV or other harmful agents and to be capable of stimulating the production of protective antibodies to HBsAg in the majority of recipients. Successful immunization of those at highest risk, e.g., babies of HBV-infected mothers, can be expected to have a major impact on the enormous, worldwide problem of hepatitis B infection and its sequelae.