Key Principles
Initial immunization strategies against hepatitis B virus (HBV) infection concentrated on high-risk groups. This strategy, which was successful in individual situations, failed to reduce the incidence and prevalence of HBV in the general population.
As a result, in 1991 the World Health Organization (WHO) has recommended that HBV universal immunization should be integrated into national immunization programs in all countries with an HBsAg prevalence of >8%.
The results of this impressive global effort have already been translated into a reduction in the incidence of HBV infection, and its complications including chronic hepatitis, cirrhosis, and hepatocellular carcinoma (HCC) in individual countries who were among the pioneers of universal infant immunization.
Yeast (and plasma)-derived HBV vaccines are highly efficacious in preventing HBV infection, and in reducing the incidence of persistent infection as well as of hepatocellular carcinoma.
Hepatitis B vaccines have had an excellent safety profile, and are generally well tolerated. Adverse reactions which are usually mild and resolve quickly tend to decrease with successive doses of the vaccine.
Despite the excellent efficacy of HBV vaccines, immunization failure may occur, and can sometimes be explained by variables such as improper storage or administration, advanced age, obesity, renal failure, chronic liver disease, and especially immunosuppression.
Another important factor that may affect non-responsiveness to HBsAg immunization seems to be genetically determined resistance.
Bypass of non-response to conventional vaccination has recently been achieved using Pre-S1/Pre-S2/S third-generation HBV vaccines.
Contraindications for HBV vaccines include hypersensitivity to yeast or any component of the vaccine. Patients who develop hypersensitivity after vaccination should not receive further injections of the vaccine.
Actively pursued research avenues intended to stimulate TH1 immune responses, include the development of more potent adjuvants as compared to the currently used aluminum hydroxide as well as development of DNA vaccines.