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PREVENTION OF HEPATITIS B
VIRUS INFECTION AND ITS RELATED DISEASES BY VACCINATION
Mei-Hwei Chang, M.D.
Department of Pediatrics, College of Medicine, National Taiwan
University,
Taipei, TAIWAN
Hepatitis B virus (HBV) infection is closely related to chronic
liver diseases
and hepatocellular carcinoma (HCC). Approximately two billion people
in the world have been infected by HBV, and 350 million of them
became chronic hepatitis B surface antigen (HBsAg) carriers. The
peak age for HCC is between 40 to 60 years in most areas, while the
peak age of HCC is younger in Africa. In hyperendemic areas for HBV,
most of the complications of chronic HBV infection develop in
adulthood,while primary HBV infection occurs mainly during infancy
or early childhood [1].
HBV infection is prevalent in Asia, Africa, Southern Europe and
Latin America,
where the HBsAg seropositive rates range from 2 to 20%. In those
hyperendemic areas, HBV infections occurs mainly during infancy and
early childhood. HCC is an important health problem in those who
have been infected early in their lives.
Infection during early childhood is a very important event leading
to chronicity of the condition and to complications. In Taiwan , the
HBsAg carrier rate in the general population is approximately 10 to
20%. Before the implementation of universal HBV vaccination program,
the HBsAg seropositive rate was 5% in infants, and increased to 10%
at 2 years of age, remaining stationary thereafter[1]. However, the
infection rate reflected by anti-HBc seropositivity, reaches 50% by
the age of 15 years. This suggests that most chronic HBsAg carriers
are infected before 2 years of age in this population [1]. In rural
Senegal, by the age of 2 years, 25% of children are infected, while
at age 15, the infection rate rises to 80% 2.
In hyperendemic areas in Asia, perinatal transmission through HBsAg
carrier
mothers accounts for 40-50% of HBsAg carriers. Around 90% of the
infants of
hepatitis B e antigen (HBeAg) seropositive carrier mothers became
HBsAg
carriers 3, irrespective of a high or low HBsAg carrier rate in the
population. Age of
infection is an important factor determining the outcome of
infection. The other
transmission route is horizontal transmission, mainly through highly
infectious family
members, such as elder siblings, and improperly sterile needles or
syringes.
Current therapies for hepatitis B, liver cirrhosis and HCC are not
satisfactory.
Immunoprophylaxis is thus the best way to get rid of the threat of
HBV infection
and its related HCC. The optimal timing for immunoprophylaxis
against HBV
infection and its related HCC is during neonatal period or early
infancy.
Correspondence: Dr Mei-Hwang Chang, No. 7, Chung-Shan S.
Road, Department of Pediatrics, National Taiwan University Hospital,
Taipei, TAIWAN
Telephone No. : (886-2)-23123456, ext. 5131
Fax: (886-2)-2-23938871 E-mail: mhchang@ha.mc.ntu.edu.tw
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