Persistence of vaccine-induced antibodies to hepatitis B surface antigen and the need for booster vaccination in adult subjects.

Protection against hepatitis B virus infection can be achieved by the induction of neutralizing antibodies against the hepatitis B surface antigen (HBsAg). An antibody concentration of 10 IU/l, as measured by radioimmunoassay, is considered to be protective. HBsAg can be produced either from the plasma of chronic carriers or by DNA recombinant technology in yeast cells. Plasma- and yeast-derived vaccines have been compared in several studies and their immunological properties were found to be similar, including the persistence of antibodies induced by either type of vaccine. Finally, yeast-derived hepatitis B vaccine can boost anti-HBs responses initially elicited by either plasma- or yeast-derived vaccine equally and effectively. In order to maintain protective immunity after hepatitis B vaccination, antibody determination and, if necessary, booster vaccination should be performed, particularly in high-risk persons.