An estimated 700,000 to 2.2 million people in the United States have chronic HBV infection. People at high risk for HBV infection include those from regions in which 2 or more of every 100 people have HBV infection. Currently, such regions include China, sub-Saharan Africa, and Southeast Asia. People with HIV infection, injection drug users, household contacts of people with HBV infection, and men who have sex with men are also at high risk for HBV infection. Vaccination can prevent HBV infection, and an increasing proportion of the U.S. population is vaccinated, including routine vaccination of infants.