At
present B vaccination policies vary by province across Canada. All provinces
include some form of universal vaccination, offered either to all newborns,
or to adolescents, as well as vaccination of individuals at high risk of
acquiring hepatitis B. Since high risk situations are not always adequately
identified, there is a risk that some susceptible individuals will not
receive vaccination. Strategies aimed at pre-teens fail to protect against
horizontal transmission in children who reside in communities where hepatitis
B is endemic. Recent data indicate that in endemic countries horizontal
transmission is more common than previously recognized. Horizontal transmission
has also been shown to occur at a high rate in South East Asian and other
immigrant communities in North America (
110-112).
The objectives of a universal hepatitis B vaccination policy should be
to
eliminate vertical (mother to child) transmission, as well as
horizontal transmission in early childhood. The policies should also protect
against hepatitis B risks imposed by environment, behaviours, or occupation.
The
vaccination strategy for Canada should be universal vaccination of all
neonates, combined with screening of all pregnant women. Newborns of infected
mothers should be given hepatitis B immunoglobulin in addition to the vaccine.
A catch up program should be instituted for all children and young adults
who have not yet been vaccinated. There should be a standardized national
policy, so that vaccination is assured for all children when their families
move between provinces.
The
seroconversion rate after hepatitis B vaccination in healthy young adults
is >90% and children > 98%. Therefore,
serologic testing post-immunization
is not recommended routinely. It is recommended, however, for
those with continual or repeated exposures. This would apply to infants
of infected mothers, sexual partners of chronic carriers and those with
occupational exposure. For further details see the Canadian Immunization
Guide, Fifth edition, 1998 (
113).
HEPATITIS
A VACCINATION
The
age distribution and number of hepatitis A-susceptible individuals in Canada
has changed over the last twenty years. An increasing percentage of adults
have never been exposed to hepatitis A and remain at risk of infection.
Hepatitis A in childhood is usually a trivial disease.However, in adults
hepatitis A can be severe with considerable morbidity, and even mortality.
In addition, some studies have suggested that acute hepatitis A infection
in patients with chronic liver disease may also cause severe disease, including
death (
114). However,
it is not clear whether the risk of severe hepatitis A is related to the
severity of the underlying liver disease or to other factors.
Hepatitis A vaccines
are safe and effective.Patients with compensated cirrhosis appear to respond
adequately to the hepatitis A vaccine (
115).
Current recommendations by NACI with regard to populations in whom
vaccination is appropriate remain pertinent (
116).These
are listed in table 7.
Table
7 Recommended usage for pre-exposure prophylaxis against hepatitis A.
|
Potential
candidates for the vaccine are
|
|
Travelers
to countries where hepatitis A is endemic, especially when travel involves
rural or primitive conditions
|
|
Residents
of communities with high endemic rates or recurrent outbreaks of HAV
|
|
Members
of the armed forces, emergency relief workers and others likely to be posted
abroad at short notice to areas with high rates of HAV infection
|
|
Residents
and staff of institutions for the developmentally challenged where there
is an ongoing problem with HAV transmission
|
|
Inmates
of correctional facilities in which there is an ongoing problem with HAV
infection
|
|
People
with life-style determined risks of infection, including those engaging
in oral or intravenous illicit drug use in unsanitary conditions
|
|
Men
who have sex with men
|
|
People
with chronic liver disease who may not be at increased risk of infection
but are at increased risk of fulminant hepatitis A
|
|
Others,
such as patients with hemophilia A or B receiving plasma-derived replacement
clotting factors; zoo-keepers, veterinarians and researchers who handle
non-human primates; certain workers involved in research on hepatitis A
virus or production of hepatitis A vaccine.
|
The cost effectiveness
of a universal strategy of hepatitis A vaccination in Canada is not known.There
is limited information on the long-term benefit of hepatitis A vaccination
in patients with chronic liver disease. Although universal vaccination
for hepatitis A is a worthy goal its role in any unified strategy for disease
prevention remains to be determined.
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