NEW APPROACHES TO HEPATITIS-A AND HEPATITIS-B VACCINES

Plasma-derived vaccines and yeast-derived recombinant Vaccines against hepatitis B virus (HBV) infection have gained an acceptable record of efficacy. However, non- or hyporesponsiveness to immunization does no t only occur in cases of obesity, renal failure or immune suppression, but also in healthy individuals. There is therefore a rationale for d eveloping more immunogenic vaccines against HBV, especially for those populations who are potential non- or hyporesponders. Currently used r ecombinant hepatitis B vaccines consist of antigen particles assembled with the product of 226 amino acids encoded in the S gene. Since prot eins encoded in the pre-S gene are also incorporated in the HBV envelo pe, pre-S gene products should, at least in theory, be useful in impro ving protection with hepatitis B vaccines. Inactivated hepatitis A vac cines are more potent than currently used hepatitis B vaccines. Two in jections of a standard dose of HAVRIX (SB) by the intramuscular route, or even a single injection using a higher dose (HAVRIX 1440), will ac hieve protective levels of antibodies. Therefore, increased potency is not essential with inactivated hepatitis A vaccines. New hepatitis A vaccines are likely to be recombinant or attenuated live types. Anothe r aspect of the improvement of existing hepatitis A and B vaccines is unification into a combined form.