Department of Pediatrics, National
Taiwan University Hospital, Taipei, (Chinese Taipei)
Viral hepatitis
can cause acute and chronic liver diseases, Prevention of hepatitis virus infection
has entered a new era after the use of vaccines.
Hepatitis A
vaccine has been proved to produce long-term immunity. The HAV vaccines
currently in clinical use are formalin-inactivated. It has been shown to be
highly immunogenic and safe, with mild and tolerable side effects. A five-year
follow-up study of HAV vaccination given to children in a schedule of 0,1,6
months showed a seroconversion rate of 95% after one dose and 100% after the
second dose of vaccine (at 6,7 months and 1 to 5 years). Two-dose schedule
(with double dosage) at 0 and 6 months has now been recommended for rapid
introduction of immunity. The effective control of hepatitis A endemics in
Taiwan mountain areas is a good example. Universal HAV vaccination has been
launched in Israel.
Integration of
hepatitis B vaccination program into the Expanded Program of Immunization (EPI)
has been conducted in more than 110 countries in the world.
Taiwan established
the first world universal HBV vaccination program in 1984. It has effectively
reduced the HbsAg carrier rate from 10 to 20% down to 0.8to 1.7% in children
below 15 years of age who were born after the vaccination program. In addition,
the incidence of liver cancer also declined form 0.52 to 0.13 per 100,000 in
children pf 6 to 14 years. Boys are more benefited than girls in liver cancer
prevention by the hepatitis B vaccination program.
The causes of
failure of the hepatitis B vaccination program are (1) poor host immune
response to hepatitis B vaccine, (2) intrauterine infection, (3) vaccine escape
mutant, (4) ignorance, (5) inadequate resources, or (6) competition of new
vaccines. We are anticipating the success pf vaccine development for hepatitis
C virus and hepatitis E virus, and to overcome the problems of vaccine failure
in hepatitis B vaccination.