Inactivated hepatitis A vaccines were developed in the 1980s and were introduced during the early 1990s. The Aventis Pasteur (AvP) inactivated hepatitis A virus antigen is used in several different vaccine formulations licensed for adults and children. Presented here are the immunogenicity results compiled from 37 clinical trials performed in 20 different countries between 1991 and 2001 in which these vaccines were administered to adults (16 years of age and over), children (aged 12 months-17 years), and infants (younger than 12 months). The accumulated clinical experience with these hepatitis A virus-containing vaccines demonstrates the excellent immunogenicity of this antigen in a wide range of situations. As with other licensed inactivated hepatitis A vaccines, immunological priming is achieved in virtually all vaccinees after a single-dose primary immunization, and it may be reinforced by a booster vaccination administered 6-36 months after the primary vaccination.