The primary purpose of the original study was to assess whether the protection afforded by the paediatric dose of Epaxal vaccine against hepatitis A was not inferior to the protection afforded by the standard dose of Epaxal. The aim of the follow-up phase was to perform a computer based modelling analysis of the long term protection afforded by the paediatric dose, and to compare this with the standard dose and also with an alternative hepatitis A vaccine (Havrix Junior).