A shot at hepatitis prevention.

Recent trends suggest that the prevalence of hepatitis infection has declined in populations vaccinated against the hepatitis viruses. Still, with an estimated 20,000 new infections annually in the United States from human hepatitis A virus, as many as 100,000 annual cases of acute infection from hepatitis B virus, and more than 1 million individuals with chronic hepatitis B virus infection, there is room for further improvement. Although hepatitis A virus infection causes debilitating symptoms and illness, it is typically not a protracted illness, and it usually resolves over weeks to months without further sequelae. By contrast, hepatitis B may convert to a chronic infection that leads to cirrhosis and hepatocellular carcinoma, underscoring the importance of vaccinations in at-risk individuals.