The evolution, implications, and applications of the hepatitis B vaccine.

The Centers for Disease Control (CDC) estimates that there are 200,000 new cases of hepatitis B virus (HBV) infection annually in the United States. Approximately 25% of patients have overt disease and about 10,000 require hospitalization; 1% to 2% of those hospitalized die during the acute phase of their disease. Of those infected, 5% to 10% (10,000 to 20,000 per year) become chronic HBV carriers, adding to the approximately 800,000 hepatitis B carriers in the United States alone. Among these carriers, cirrhosis or hepatocellular carcinoma will develop in some; HBV infection is a major cause of nonalcoholic cirrhosis, and the CDC estimates that there are almost 4,000 deaths per year from cirrhosis among chronic HBV carriers. It has also been estimated that hepatitis B, in terms of hospitalization, other medical expenses, and time lost from work, costs the US economy $750 million per year. Recognizing that the United States is