Immunogenicity of a combined hepatitis A and B vaccine in healthy young adults

Combining several vaccines in a single formulation can change the potency of the vaccine antigens. Previous studies suggested a higher immunogenicity of a new combined hepatitis A and B vaccine compared with the monovalent hepatitis B vaccine. We investigated the immune response to hepatitis B surface antigen 1 month after the third vaccine dose in 282 healthy adults who had received either a monovalent hepatitis B vaccine (n=148) or the combined hepatitis A/B vaccine (n=134). A slight trend towards higher geometric mean titres of anti HBs was found at this point in time in the group immunised with the combined vaccine, especially in the few vaccinees with preexisting antibodies against hepatitis A virus. However none of these differences was statistically significant, arguing against an advantage of the combined vaccine regarding hepatitis B immunisation.