The early
clinical trials based on the use of the conventional
prophylactic HBV vaccine (HBsAg) were unable to
show any clinical benefit either when tested alone
[26] or in combination with direct antiviral therapy
[27]. Failure was believed to be attributable to the
use of a single HBV antigen and to the type of
adjuvant that was not efficient in generating
CD8þT-cell responses [25]. However, new vaccine
formulations (HBV envelope-expressing DNA
vaccine or peptide-based vaccines) that elicit HBVspecific
CD8þT-cell responses in healthy volunteers
or in CHB patients [28] were unable to achieve
therapeutic effects in patients