Worldwide about 350 million people are chronic carriers of the hepatitis B virus (HBV).
The infection can cause acute and chronic liver disease including cirrhosis and hepatocellular
carcinoma (HCC). Hepatocellular injuries of HBV infection are predominantly immune-mediated,
and the natural history of chronic infection can be divided into three phases based
on virus-host interactions-namely, immune tolerance, immune clearance, and viral integration
phases. Four serotypes (adw, ayw, adr, and ayr) and seven genotypes (A to G) of HBV
have been identified, and they show some distinct geographic distributions. The HBV
genotypes may have clinical relevance and are currently under investigation. On the
basis of disease burden and the availability of safe and effective vaccines, the WHO
recommended that by the end of the 20th century hepatitis B vaccine be incorporated
into routine infant and childhood immunisation programmes for all countries. The efficacy
of universal immunisation has been shown in different countries, with striking reductions
of the prevalence of HBV carriage in children. Most important, hepatitis B vaccination
can protect children against HCC and fulminant hepatitis, as has been shown in Taiwan.
Nevertheless, the implementation of worldwide vaccination against HBV requires greater
effort to overcome the social and economic hurdles. Safe and effective antiviral treatments
are available but are still far from ideal, a situation that, hopefully, will be improved
soon. With hepatitis B immunisation, the global control of HBV infection is possible
by the end of the first half of 21st century.