Efficacy of Hepatitis B Vaccine in Chimpanzees Given Transfusions of Highly Infective Blood

The protective efficacy of a hepatitis B vaccine against infections from transfusions of large volumes of highly infective blood in five immunized chimpanzees was assessed. Hepatitis B surface antigen (HBsAg) became positive and antibody to HBsAg (anti-HBs) disappeared soon after transfusion in the five chimpanzees. Two chimpanzees that had HBsAg only on the day of transfusion did not develop infection. However, the re-maining three chimpanzees with persistent HBsAg antigenemia for three to four days developed serologic evidence of infection. Two chimpanzees did not have hepatitis and the third had a mild, transient case of acute hepatitis. The hepatitis B vaccine prevented the four immunized chimpanzees from developing illness. The remaining chimpanzee developed hepatitis, but a rapid booster response of anti-HBs owing to the previous vac-cination appeared to lighten the severity of the disease and prevent chronicity. Recent advances in the study of hepatitis B virus (HBV) have provided the means for the prevention of infection. Recent animal and clinical studies have established the safety and efficacy of HB