world cancer report - iarc

8% = High prevalence
2% - 8% = Intermediate prevalence
< 2% = Low prevalence
Fig. 4.15 Global prevalence of chronic hepatitis B virus (HBV) infection 1997,
based on HB surface antigen serology.
blood products, sharing contaminated
needles during intravenous drug use and
through sexual transmission.
Currently, there are around 350 million
chronic carriers of HBV worldwide and,
based on conservative assumptions, an
estimated 70 million of these individuals
are likely to die from HBV-related liver disease.
Because of the relatively low cost of
the hepatitis B vaccine and the uniformly
fatal outcome of hepatocellular carcinoma,
childhood hepatitis B vaccination in
highly HBV endemic areas is one of the
most cost-effective measures available for
prevention of early mortality in adults [2].
Nature of the intervention
Vaccination efforts have historically concentrated
on preventing acute infectious
diseases, particularly those of childhood.
Hepatitis B vaccine is the first vaccine
designed to prevent a major human cancer
and currently the only one in widespread
use. The vaccine was initially
developed by purifying the viral envelope
component of the surface antigen particle
(HBsAg) of the virus from the blood of individuals
with chronic HBV infection. This
plasma-derived vaccine undergoes intensive
treatment to destroy any live virus, as
well as to remove any other potential contaminants,
and is then combined with an
alum adjuvant to stimulate the immune
system. Second-generation vaccines
involved production of HBsAg particles
through yeast or mammalian cells using
recombinant DNA technology. Both plasma-derived
and DNA recombinant vaccines
are equally safe and effective. Since
the early 1980s, hundreds of millions of
doses of hepatitis B vaccine have been
administered worldwide. Adverse reactions
are uncommon and generally mild in
nature, with this vaccine considered
among the safest of vaccines. Hepatitis B
vaccine is generally administered in
sequential doses with at least four weeks
between doses. An appropriate response
to the vaccine is the development of antibodies
to the surface antigen and is
termed seroconversion. Three doses of
vaccine will generally produce seroconversion
rates in excess of 90%.
Vaccination campaigns aimed at reducing
HBV-related hepatocellular carcinoma must
take into consideration the patterns of HBV
transmission. Because the highest risk for
development of chronic HBV carriage occurs
at the youngest ages, hepatitis B vaccine is
most efficacious when given as close to
birth as possible. This early vaccination benefit
will be most pronounced in those highendemicity
countries with significant mother-to-child
and early horizontal transmission.
Hepatitis B vaccine does not interfere with
other vaccines and can be administered
simultaneously with many of the other routine
childhood immunizations, including
diphtheria, tetanus and whole-cell pertussis
vaccine, oral attenuated poliomyelitis vac-
No routine immunization
Routine immunization
Fig. 4.16 Global distribution of countries using HBV vaccine in their national
immunization programme, 2000.
cine and BCG (bacille Calmette-Guérin).
Integration of hepatitis B vaccine into the
routine “Expanded Programme on
Immunization” (EPI) efforts of individual
countries provides the most appropriate
strategy for global hepatitis B vaccination.
In addition to the focus on hepatitis B vaccination
to prevent primary infection with
HBV, new therapeutic vaccines have been
designed to treat chronic HBV carriers and
hopefully prevent progression to cirrhosis or
cancer. Several novel vaccines, including
DNA-based vaccines which incorporate the
hepatitis B surface antigen gene, have been
designed to stimulate the immune system of
HBV-infected individuals, through induction
of either a T-cell response or production of
neutralizing antibodies [3]. Although therapeutic
vaccines demonstrate potential,
these trials are in the earliest stages and it
remains to be seen what level of efficacy in
reducing or stopping HBV replication and
preventing progression can be achieved. The
frequency and degree of serious adverse
effects from these vaccines must also be
demonstrated to be acceptably low.
Implementation of preventive measures
In the early 1990s, WHO/EPI recommended
integration of hepatitis B vaccination
into the routine EPI and this was subsequently
endorsed by the World Health
Assembly. Earlier, hepatitis B vaccine was
utilized sporadically, with fewer than 20
countries routinely administering the vac-
Hepatitis B vaccination 145