In this study, 15 subjects per vaccine will be recruited to receive immunization with one of two hepatitis B vaccines, Engerix B or Fendrix, representing exactly matched antigens (hepatitis B surface antigen) but discordant adjuvant technologies. Following a screening visit, subjects will be randomly allocated to receive three doses of a vaccine at 0, 1 and 2 months. Innate immune responses (cytokine levels and whole blood gene expression) after doses #1 and #3 and adaptive immune responses (serum antibody and antigen specific cellular responses) will be measured at various timepoints after immunisation on an outpatient basis.