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Hepatitis, Viral, Type B
Description
Hepatitis B is a viral infection with
clinical manifestations that include anorexia, abdominal discomfort, nausea,
and vomiting, and often progresses to jaundice. Severity ranges from
inapparent infections detectable only by elevated liver function tests to
fulminating, fatal cases of acute hepatic necrosis.
Hepatitis B virus (HBV) is transmitted
primarily through activities that involve contact with blood or
blood-derived fluids. The most frequent mode of transmission is through
sexual activity, either heterosexual or homosexual, between an infected and
a susceptible person. Principal activities that can result in blood exposure
include working in health care fields (medical, dental, laboratory, or
other) that entail direct exposure to human blood; receiving blood
transfusions that have not been screened for HBV; and having dental,
medical, or other exposure to needles (for example, acupuncture, tattooing,
or injecting drug use) that are contaminated with HBV. In addition, open
skin lesions in children or adults, due to factors such as impetigo,
scabies, and scratched insect bites, can play a role in disease transmission
if direct exposure to wound exudates occurs.
Occurrence
The prevalence of chronic HBV
infection is high (>8%) in all socioeconomic groups in certain areas
(see Map 3-3): all of Africa; Southeast Asia,
including China, Korea, Indonesia, and the Philippines; the Middle East,
except Israel; south and western Pacific islands; the interior Amazon River
basin; and certain parts of the Caribbean (that is, Haiti and the Dominican
Republic). The prevalence of chronic HBV infection is intermediate (2% to
7%) in south central and southwest Asia, Israel,
Japan, eastern and southern Europe,
Russia, most areas surrounding the Amazon River basin, Honduras, and
Guatemala. In northern and western Europe, North America, Australia, New
Zealand, Mexico, and southern South America, chronic HBV infection
prevalence is low (<2%) in the general population.
Risk for Travelers
The risk of HBV infection for
international travelers is generally low, except for certain travelers in
countries with intermediate or high HBV endemicity. Factors to consider in
assessing risk include (1) the prevalence of chronic HBV infection in the
local population; (2) the extent of direct contact with blood or secretions,
or of sexual contact with potentially infected people; and (3) the duration
of travel.
Preventive Measures
Vaccine
HBV vaccination is currently
recommended for all people who work in health care fields (medical, dental,
laboratory, or other) that entail exposure to human blood. HBV vaccination
should be considered for travelers who plan to reside for 6 months or longer
in areas with intermediate to high levels of endemic HBV transmission (that
is, with HBV surface antigen [HbsAg] prevalence >2%) and who will
have any of the previously discussed types of contact with the local
populations. In particular, travelers who anticipate sexual contact or who
will have daily physical contact with the local population; or who are
likely to seek medical, dental, or other treatment in local facilities; or
any combination of these activities during their stay should be advised to
receive the vaccine. Those who will be traveling for less than 6 months
should also be vaccinated if they will have direct contact with blood, or
sexual contact with residents of areas with intermediate to high levels of
endemic HBV transmission.
Two types of HBV vaccines have been
licensed in the United States. One, which was manufactured from the plasma
of people with chronic HBV infection, is no longer produced in the United
States. The remaining available type of vaccine is produced through
recombinant deoxyribonucleic acid (DNA) technology by common baker's yeast
into which the gene for HbsAg has been inserted. This type of HBV vaccine
has been shown to be very safe when given to people of all ages.
The usual schedule of primary
vaccination consists of three intramuscular doses of vaccine. The
recommended dose varies by product and the recipient's age (Table
3-7). The vaccine is usually administered as a three-dose series on a
0-, 1-, and 6-month schedule. The second dose should be given 1 month after
the first dose; the third dose should be given at least 2 months after the
second does and at least 4 months after the first dose. Alternatively, the
vaccine produced by GlaxoSmith-Kline licensed to be administered on a
four-dose schedule at 0, 1, 2, and 12 months. There is also a two-dose
schedule for a vaccine produced by Merck & Co., Inc. that has been licensed
for children and adolescents 11 through 15 years of age. Using the two-dose
schedule, the adult dose of Recombivax-HB® is administered, with
the second dose given 4 to 6 months after the first dose.
Table 3-7.--Recommended Doses of Currently
Licensed Hepatitis B Vaccines.
| Group |
Dose |
| Recombivax-HB®* |
Engerix-B®* |
All infants (regardless of mother’s
HBsAg status), children,
adolescents, and adults, birth
through 19 years of age. |
5 µg |
10 µg |
| Adults 20 years of age or older.† |
10 µg |
20 µg |
Dialysis patients and other
immunocompromised people. |
40 µg§ |
40 µg¶ |
Vaccination should ideally begin at
least 6 months before travel so the full vaccine series can be completed
prior to departure. Because some protection is provided by one or two doses,
the vaccine series should be initiated, if indicated, even if it cannot be
completed prior to departure. However, optimal protection is not conferred
until after the final vaccine dose. There is no evidence of interference
between HBV vaccine and other simultaneously administered vaccine(s) or with
immune globulin. The optimum site of injection in adults is the deltoid
muscle; vaccination in the buttocks results in poorer antibody response.
Long-term studies of healthy adults and children indicate that immunologic
memory remains intact for at least 15 years and confers protection against
chronic HBV infection, even though HBV surface antibody (anti-HBVs) levels
can become low or decline below detectable levels. For children and adults
whose immune status is normal, booster doses of vaccine are not recommended,
nor is serologic testing to assess antibody levels necessary for most
vaccinees. (See Vaccine
Recommendations for Infants and Children for a discussion of the HBV
immunization schedule for infants who will be traveling.)
Adverse Reactions
Pain at the injection site (3% to 29%)
and elevated temperature >37.7° Celsius (>99.9° Fahrenheit) (1% to 6%) are
the most frequently reported side effects among vaccine recipients. In
placebo-controlled studies, these side effects were reported no more
frequently among people receiving HBV vaccine than among people receiving
placebo. Among children receiving both HBV vaccine and
diphtheria-tetanus-pertussis (DTP)
vaccine, these mild side effects have been observed no more frequently than
among children receiving DTP vaccine alone.
A low rate of anaphylaxis has been
observed in vaccine recipients based on reports to the Vaccine Adverse Event
Reporting System (VAERS) (with an estimated incidence of 1 case in 600,000
vaccine doses distributed); 2 anaphylaxis cases were in children. None of
the people who developed anaphylaxis died; however, anaphylaxis can be fatal
and HBV vaccine can, in very rare instances, cause a life-threatening
hypersensitivity reaction in certain individuals. Therefore, further
vaccination with HBV vaccine is contraindicated in people with a history of
anaphylaxis after a previous dose of vaccine.
In the United States, surveillance of
adverse events has shown a possible association between Guillain-Barré
syndrome (GBS) and receipt of the first vaccine dose of plasma-derived HBV
vaccine in adults. However, analysis of GBS reported to the Centers for
Disease Control and Prevention (CDC), U.S. Food and Drug Administration
(FDA), and vaccine manufacturers for the estimated 2.5 million adults who
received one or more doses of recombinant HBV vaccine from 1986 to 1990 did
not demonstrate an association between receipt of recombinant vaccine and
GBS.
Case reports of other rare adverse
events following HBV vaccination that have been published in the medical
literature have included multiple sclerosis, optic neuritis, rheumatoid
arthritis, type I diabetes, autoimmune disease, and alopecia. Most of these
reported adverse events have been in adults and no studies have compared the
frequency of occurrence of the purported vaccine-associated disease or
syndrome with the frequency of occurrence in an unvaccinated population.
Analysis of reports to the VAERS has not found an increased frequency of
adverse events among children since implementation of routine infant HBV
vaccination.
Any presumed risk of adverse events
associated with HBV vaccination must be balanced with the expected 5,000
deaths from HBV-related liver disease that would occur in the United States
each year without immunization, assuming a 5% lifetime risk of HBV
infection. Surveillance for vaccine-associated adverse events will continue
to be an important part of HBV vaccination programs in spite of the current
record of safety.
Precautions and Contraindications
On the basis of limited data, there is
no apparent risk of adverse events to the developing fetus when HBV vaccine
is administered to pregnant women. The vaccine contains noninfectious HBsAg
particles and should cause no risk to the fetus. HBV infection affecting a
pregnant woman can result in serious disease for the mother and chronic
infection for the newborn. Therefore, neither pregnancy nor lactation should
be considered a contraindication for vaccination.
Other
Behavioral preventive measures are
similar to those for human immunodeficiency virus and acquired
immunodeficiency syndrome (see "Acquired Immunodeficiency Syndrome (AIDS)").
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