Project to Evaluate Hepatitis B Vaccine-induced Immunity Among US-born Adolescents Who Received Hepatitis B Primary Vaccination Series During Early Childhood

The aims of this study are to determine:

1. the degree of immunity against hepatitis B,
2. factors associated with immunity against hepatitis B,
3. if the amount of antigen provided in a booster dose (used to measure the degree of immune memory) affects the body's response to the booster, and
4. if the age at which the vaccination was initiated during infancy affects duration of protection against hepatitis B among adolescents 16-19 years of age born in the United States who were immunized against hepatitis B as infants. These data will be important to evaluate the potential need for a possible booster dose of hepatitis B vaccine among adolescents.

Study subjects eligible for enrollment will:

• have blood drawn for baseline serologies
• receive the hepatitis B booster dose (randomly determined to be either a 10 ug or 20 ug dose)
• have blood drawn again 14 days later to determine if the booster dose has engendered an anamnestic response (a response attributed to prior immunity rather than a new response to the vaccine)

The primary hypothesis is that the majority of young people will exhibit immune memory for hepatitis B in response to a booster dose of vaccine.