New vaccination strategies for low- and non-responders to hepatitis B vaccine.

The currently available recombinant hepatitis B vaccines are safe, efficacious and immunogenic. Nevertheless, a high rate of low- and nonresponsiveness to the current vaccine poses a problem since this group remains susceptible to infection with hepatitis B virus. Efforts are underway to develop new vaccines and strategies to enhance seroprotection rates. One possibility under investigation is the low-dose intradermal administration of vaccine since the immune system is well represented in both the epidermis and the dermis. Despite encouraging results concerning the immunogenicity in previous non-responders, the main difficulty is the technique of administration and unacceptable local adverse effects. Promising data have emerged from clinical trials evaluating the immunogenicity of new recombinant vaccines containing the complete pre-S1 and pre-S2 regions of HbsAg and, more recently, of novel adjuvanted hepatitis B vaccines. Future approaches include DNA vaccination and expression of HbsAg determinants in live recombinant vectors.