Hepatitis A & B Immunizations
Medical Author: Mary D. Nettleman, MD, MS, MACP
Medical Editor: Jay W. Marks, MD
Introduction to hepatitis
The term 'hepatitis' means inflammation of the liver. Hepatitis can be caused
by viruses, other
infectious agents, alcohol, and other chemicals. The two viruses that most
commonly infect the liver are the hepatitis A virus and the hepatitis B virus.
Although their names are similar, these viruses are not related. They differ in
the way they are transmitted from person to person and their ability to cause
chronic infection.
Hepatitis A
Hepatitis A is caused by a virus which is spread predominately through the
fecal-oral route when small amounts of infected fecal matter are inadvertently
ingested. Infected individuals shed large amounts of the virus in their stool,
starting about two weeks before symptoms present, and continue shedding the
virus in their stool for one to three
months.
- Close contact with an infected person increases the chances of
contracting
the virus.
- Children are particularly contagious because they have lower
standards of hygiene and may not appear sick.
- The hepatitis A virus also may be
spread by ingestion of food or water that is contaminated by infected
individuals.
- Much less commonly, contaminated needles or blood may spread
hepatitis A.
Some patients with hepatitis A infection have no symptoms, and
these asymptomatic infections
are more common in children.
Most adults experience symptoms including:
Although the
symptoms resolve over several weeks, fatigue can be prolonged. Rarely, viral
hepatitis caused by hepatitis A can lead to liver failure, coma and death.
Hepatitis A does not cause chronic or persistent
infection of the liver. Once a person has recovered from hepatitis A, he or she
is immune to reinfection with
hepatitis A for life. This is true because effective antibodies are developed
against the hepatitis A virus. After infection with hepatitis A, these
antibodies provide life-long protection against the virus. The ability of the
body to make protective antibodies after infection with hepatitis A led
researchers to develop vaccines against the disease.
Hepatitis A vaccine is made of killed hepatitis A viruses and causes the
body's immune system to produce antibodies against the hepatitis A virus. In 94% to 100%
of vaccine recipients, antibodies start to develop immediately after the first
dose but do not reach protective levels for 2 to 4 weeks. A second dose of the
vaccine is recommended at least six months after the first dose to provide
prolonged protection.
Two hepatitis A vaccines are currently available in the
United States; these vaccines are
hepatitis a vaccine injection
(Havrix and Vaqta). The vaccine is given
as an injection into the deltoid muscle of the arm. Both Havrix and Vaqta
provide high level protection against hepatitis A. There is also a combination
vaccine called
hepatitis-b-hepatitis-a-vaccine injection (Twinrix) that protects against both hepatitis A and hepatitis B.
The dosing schedule for Twinrix is different from the other hepatitis A vaccines
and requires three doses over six months.
In the United States, hepatitis A
vaccination is recommended for all children
at one year of age. Vaccination also is recommended for individuals in high-risk
settings. Examples include:
Side effects of the hepatitis A vaccine usually are
mild. Soreness at the site of injection is common. Less commonly, recipients may
complain of headache
or fatigue. Serious allergic reactions are possible, but are rare.
A second option for protecting people against hepatitis A is to administer
antibodies that are already programmed to attack the virus. When people donate
blood, the part of the blood carrying antibodies (the 'immune globulin'
fraction) can be separated. Because some blood donors are likely to have
antibodies against the hepatitis A virus, pooled immune globulin from many
donors is likely to contain antibodies against hepatitis A. This immune globulin
can be injected into a person at risk for hepatitis A and will provide immediate
but temporary protection against infection. Protection with immune globulin
lasts two to four months depending on the dose. Immune globulin is used when
immediate protection against hepatitis A is required. An example would be
someone who is leaving immediately to travel to rural areas of a developing
country. Such a traveler would also receive hepatitis A vaccine but would not
have time to develop antibodies before departure. Immune globulin sometimes is
in short supply and should be used only when necessary.
- If an unvaccinated person is exposed to hepatitis A, he or she should be
given the vaccine or immune globulin as soon as possible.
- Vaccine is used for
exposed persons aged one to 40 years.
- Immune globulin currently is recommended
for exposed persons over the age of 40 years.
These measures will reduce the
risk that the exposed person will contract hepatitis A by 85% to 90% if given
within two weeks of exposure.
Next: Hepatitis B »
- hepatitis b vaccine-injection, Engerix-B, Recombivax HB - Consumer information about the medication HEPATITIS B VACCINE - INJECTION (Engerix-B, Recombivax HB), includes side effects, drug interactions, recommended dosages, and storage information. Read more about the prescription drug HEPATITIS B VACCINE - INJECTION.
- Childhood Vaccination Schedule - Read our printable children's immunization schedule and learn about vaccines for kids (Hib, polio, DTaP, MMR, HPV, flu, chickenpox, meningitis, rotavirus, pneumonia, hepatitis A and B).
- Liver Cancer - Get information on liver cancer, its symptoms, causes, diagnosis, staging, prognosis, treatment, and prevention.
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