Taiwan has launched a successful nationwide neonatal hepatitis B immunization since July 1, 1984. It successfully decreased the incidence of hepatitis B virus infection, the hepatitis B carrier rate as well as liver diseases among children and adolescents. The sexual transmission route is another important way of hepatitis B infection aside from the mother and child vertical infection, especially for youth and adults. Hepatitis B vaccination cohort refers to those who were born after 1986 and received hepatitis B vaccine immunization during newborn period. They are gradually entering into young adults and adolescent age. Among them, there is no empirical evidence to show the actual infection rate and to help implement hepatitis B vaccine booster policy for those who had three seronegative viral markers of hepatitis B. Therefore, the study design is to collect three consecutive years graduate school students school entry health examination data and undergo three hepatitis B viral markers checkup and blood types. The data linkage includes their health checkup data in the freshmen period, Taiwan CDC databank for neonatal hepatitis B immunization records, pregnancy and birth record registry, Taiwan cancer registry and Taiwan death record registry.