Epaxal®: a virosomal vaccine to prevent hepatitis A infection

Over the last few decades, different types of inactivated hepatitis A virus (HAV) vaccines have been developed: several aluminum-adjuvanted vaccines and an aluminum-free, virosome-formulated vaccine. Both types of vaccines are whole-virus preparations that are produced by growth of HAV strains in human diploid cell cultures and are subsequently inactivated with formaldehyde. This review summarizes all published papers on a virosome-formulated vaccine, Epaxal, based on formalin inactivated HAV (strain RG-SB) adsorbed to the surface of special liposomes (virosomes), that replace aluminum hydroxide as the adjuvant principle. A single injection of virosomal HAV vaccine is well tolerated and highly immunogenic, with 88-97% of seroprotection 2 weeks after a first dose. HAV virosomal vaccine can be administered concomitantly with other vaccines, without inducing antigenic competition. Direct comparison with aluminum-adsorbed vaccine has shown that the immunogenicity was similar, but fewer local reactions were reported with Epaxal. Recent studies in children have demonstrated that Epaxal Junior is also an excellent HAV vaccine for mass vaccination programs.