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Hepatitis A and B Vaccinations

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What is 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 vaccine

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 most 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 arehepatitis 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:

  • travelers to developing countries,
  • men who have sex with men,
  • users of illicit drugs,
  • persons needing frequent blood products, and
  • people who have chronic liver disease.

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.

Medically Reviewed by a Doctor on 4/16/2014

Source: MedicineNet.com
http://www.medicinenet.com/hepatitis_immunizations/article.htm

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