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Hepatitis, Viral, Type B
Description
Hepatitis B is caused by the hepatitis B virus (HBV).
The clinical manifestations of HBV infection range in severity from
no symptoms to fulminant hepatitis. Signs and symptoms of hepatitis
B may include fever, malaise, anorexia, nausea, and abdominal discomfort,
followed within a few days by jaundice.
Occurrence
HBV is transmitted through activities that involve
contact with blood or blood-derived fluids. Such activities can include
unprotected sex with an HBV-infected partner; injection of illegal
drugs; work 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; or having dental,
medical, or cosmetic (e.g., tattooing or body piercing) procedures
with needles or other equipment that are contaminated with HBV. In
addition, open skin lesions, such as those due to impetigo, scabies,
or scratched insect bites, can play a role in HBV transmission if
direct exposure to wound exudates from HBV-infected persons occurs.
The prevalence of chronic HBV infection is low (<2%)
in the general population in Northern and Western Europe, North America,
Australia, New Zealand, Mexico, and Southern South America. In the
United States and many other developed countries, children and adolescents
are routinely vaccinated against hepatitis B. The highest incidence
of disease is in younger adults, and most HBV infections are acquired
through unprotected sex with HBV-infected partners or through illicit
injection drug use. The prevalence of chronic HBV infection is intermediate
(2%–7%) in South Central and Southwest Asia, Israel, Japan,
Eastern and Southern Europe, Russia, most areas surrounding the Amazon
River basin, Honduras, and Guatemala. The prevalence of chronic HBV
infection is high (>8%) in all socioeconomic groups in certain
areas: 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 (Haiti and the Dominican Republic).
Risk for Travelers
The risk of HBV infection for international travelers
is generally low, except for certain travelers in countries where
the prevalence of chronic HBV infection is high or intermediate.
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 sex contact with potentially
infected persons, and 3) the duration of travel. Modes of HBV transmission
in areas with high or intermediate prevalence of chronic HBV infection
that are important for travelers to consider are contaminated injection
and other equipment used for health care-related procedures and blood
transfusions from unscreened donors. However, unprotected sex and
sharing illegal drug injection equipment are also risks for HBV infection
in these areas.
Clinical Presentation
The incubation period of hepatitis B averages 120
days (range 45–160 days). Constitutional symptoms such as malaise
and anorexia may precede jaundice by 1–2 weeks. Clinical symptoms
and signs include nausea, vomiting, abdominal pain, and jaundice.
Skin rashes, joint pains, and arthritis may occur. The case-fatality
rate is approximately 1%. Acute HBV infection causes chronic (long-term)
infection in 30%–90% of persons infected as infants or children
and in 6%–10% of adolescents and adults. Chronic infection
can lead to chronic liver disease, liver scarring (cirrhosis), and
liver cancer.
Prevention
Vaccine
Hepatitis B vaccination should be administered to
travelers to areas with intermediate to high levels of endemic HBV
transmission (i.e., with hepatitis B surface antigen [HBsAg] prevalence >2%)
and who will have close contact with the local populations. In particular,
travelers who anticipate sex 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. Hepatitis B vaccination is currently recommended for
all United States residents who work in health-care fields (medical,
dental, laboratory, or other) that entail exposure to human blood.
Two monovalent hepatitis B vaccines are currently
licensed in the United States: Recombivax HB, manufactured Merck
and Co., Inc., and Engerix B, manufactured by GlaxoSmithKline. These
vaccines are produced through recombinant DNA technology by baker's
yeast into which the gene for HBsAg has been inserted. 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 3–8).
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 dose and at least 4 months after the first dose.
Alternatively, the vaccine produced by GlaxoSmithKline is also approved
for administration 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., which has been licensed for children and adolescents 11–15
years of age. Using the two-dose schedule, the adult dose of Recombivax-HB
is administered, with the second dose given 4–6 months after
the first dose. An interrupted hepatitis B vaccine series does not
need to be restarted. A three-dose series that has been started with
one brand of vaccine may be completed with the other brand.
Twinrix, manufactured by GlaxoSmithKline, is a combined
hepatitis A and hepatitis B vaccine licensed for persons 18 years
of age or more. Primary immunization consists of three doses, given
on a 0-, 1-, and 6- month schedule, the same schedule as that used
for single-antigen hepatitis B vaccine (Table
3–6). Twinrix consists of inactivated hepatitis A virus
and recombinant HBsAg protein, with aluminum phosphate and aluminum
hydroxide as adjuvant and 2-phenoxyethanol as a preservative.
Individual clinicians may choose to use an accelerated
schedule (i.e., doses at days 0, 7, and 14) for travelers who will
depart before an approved vaccination schedule can be completed.
The FDA has not approved accelerated schedules that involve vaccination
at more than one time during a single month for hepatitis B vaccines
currently licensed in the United States. Persons who receive a vaccination
on an accelerated schedule that is not FDA approved should also receive
a booster dose at least 6 months after the start of the series to
promote long-term immunity.
Table 3–8.
Recommended doses of currently licensed
Hepatitis B vaccines
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| All infants (regardless of
mother's HBsAg status), children, adolescents, and
adults, birth through 19 years |
5 µg |
10 µg |
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Adults 20 years of age or older |
10 µg |
20 µg |
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Dialysis patients and other
immunocompromised persons |
40 µg§ |
40 µg¶ |
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Ideally, vaccination should begin at least 6 months
before travel so the full vaccine series can be completed before 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
before departure. Optimal protection, however, is not conferred until
after the final vaccine dose. There is no interference between hepatitis
B vaccine and other simultaneously administered vaccine(s) or with IG.
The optimum site of injection in adults is the deltoid muscle. 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 hepatitis B surface antibody (anti-HBs) 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.
Serologic testing to assess antibody levels is not necessary for most
vaccinees. (See Vaccine
Recommendations for Infants and Children, for a
discussion of the hepatitis B immunization schedule for infants who will
be traveling.)
Adverse Reactions
Hepatitis B vaccines have been shown to be very safe
for persons of all ages. Pain at the injection site (3%–29%)
and elevated temperature >37.7° C (>99.9° F) (1%–6%)
are the most frequently reported side effects among vaccine recipients.
In placebo-controlled studies, these side effects were reported no
more frequently among persons receiving hepatitis B vaccine than among
those receiving placebo. Among children receiving both hepatitis B
vaccine and diphtheria-tetanus-pertussis (DTP) vaccine, these mild
side effects have been observed no more frequently than among children
receiving DTP vaccine alone. For hepatitis A vaccine (a component of
the combination hepatitis A/hepatitis B vaccine Twinrix), the most
frequently reported adverse reactions occurring within 3–5 days
were soreness or pain at the injection site (56% among adults and 8%
among children) and headache (14% among adults and 4% among children).
No serious adverse events among children or adults that could be definitively
attributed to hepatitis A vaccine or increases in serious adverse events
among vaccinated persons compared with baseline rates have been identified.
Precautions and Contraindications
These vaccines should not be administered to persons
with a history of hypersensitivity to any vaccine component, including
yeast. The vaccine contains a recombinant protein (HBsAg) that is noninfectious.
Limited data indicate that there is no apparent risk of adverse events
to the developing fetus when hepatitis B vaccine is administered to
pregnant women. HBV infection affecting a pregnant woman can result
in serious disease for the mother and chronic infection for the newborn.
Neither pregnancy nor lactation should be considered a contraindication
for vaccination.
Behavioral preventive measures are similar to those
for HIV infection and AIDS (see AIDS).
Treatment
No specific treatment is available for acute illness
caused by hepatitis B. Antiviral drugs are approved for the treatment
of chronic hepatitis B.
— Miriam
Alter, Beth Bell, Anthony Fiore, Eric Mast, Linda Moyer
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