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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:
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 (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.
Hepatitis B vaccine
Hepatitis B was previously referred to as "serum hepatitis" because it usually is spread by the transfer of infected blood or serum (for example, through needle sticks, blood transfusions, hemodialysis, and childbirth). Hepatitis B also is spread through sexual intercourse and may be passed from mother to child. Inadvertent exposure to infected blood or body fluids may occur during tattooing, body piercing, or when sharing razors or toothbrushes with an infected person. Persons infected with hepatitis B may be asymptomatic or may develop fatigue, jaundice, and weight loss. Rarely - though more commonly than with hepatitis A - acute infection with hepatitis B can cause liver failure and death.
Most infected adults are able to clear the hepatitis B virus from their body and become immune to further infections with hepatitis B. However, some people are not able to clear the hepatitis B virus and it progresses to chronic (persistent) infection and inflammation of the liver. Most infants infected at birth and 25% to 50% of infected children aged 1–5 years have chronic persistent infection.
Chronic infection may be mild or may damage the liver. The majority of individuals with chronic hepatitis B who clear the virus and are "cured" still have detectable virus in the liver. However, the importance of this fact is unclear since there is no evidence of consequences to the presence of the virus except that it can be reactivated with immunosuppression. Individuals with hepatitis B virus only in the liver are not infectious. Some people with chronic hepatitis B infection have their lives shortened by complications of liver disease, cirrhosis, or liver cancer.
Vaccination has reduced the number of new cases of hepatitis B by more than 75% in the United States. The hepatitis B vaccine contains a protein (antigen) that stimulates the body to make protective antibodies. Examples of hepatitis B vaccines available in the United States include hepatitis B vaccine-injection (Engerix-B and Recombivax-HB). Three doses (given at 0, 1, and 6 months) are necessary to assure protection.
There are also combination vaccines on the market that provide protection against hepatitis B and other diseases. For example:
- hepatitis-b-hepatitis-a-vaccine injection (Twinrix), which provides protection against both hepatitis A and hepatitis B;
- Haemophilus B/hepatitis B vaccine - injection (Comvax) provides protection against hepatitis B and Haemophilus influenzae type b (a cause of meningitis); and
- Pediarix provides protection against hepatitis B, tetanus, pertussis and polio.
Hepatitis B vaccines are effective and safe. Most vaccinated individuals develop protective antibodies when they get the vaccine and are protected from infection with hepatitis B. Among individuals at high risk for infection with hepatitis B include:
- health care workers,
- intimate and household contacts of patients with chronic hepatitis B infection,
- public safety workers who may be exposed to blood products,
- men who have sex with men,
- individuals with multiple sexual partners,
- dialysis patients,
- injection drug users,
- persons with chronic liver disease,
- residents and staff in institutions that care for persons with developmental disabilities,
- persons infected with human immunodeficiency virus (HIV), and
- persons who require repeated transfusions or blood products.
Centers that serve high-risk individuals are encouraged to provide the vaccine to their clients. Such centers include:
- dialysis units,
- drug treatment facilities,
- sexually transmitted diseases clinics and correctional facilities.
A blood test for hepatitis B antibodies is recommended after vaccination to ensure that antibodies have been produced. For the few who do not form antibodies, revaccination may improve the response, especially in infants. However, a small proportion of individuals will never respond to hepatitis B vaccination. Side effects from the vaccine usually are mild, primarily soreness at the site of injection. The risk of serious allergic reactions (anaphylaxis) is less than one per million doses.
In the United States, hepatitis B vaccination is recommended for all infants at birth. Older children and adolescents should receive the vaccine if they did not receive it at birth. Adults in high risk situations also are advised to receive hepatitis B vaccine.
Some countries have a high prevalence of hepatitis B in their population. Travelers who visit these countries for a prolonged period of time (usually 6 months or longer) and those who may be exposed to blood or semen should consider vaccination.
Unvaccinated individuals who are exposed to a known case of hepatitis B or to a person at high risk for hepatitis B should be evaluated by a physician. Examples of such exposures include needle stick injuries in health care workers or sexual intercourse with an infected person. If the exposure is significant, the physician will recommend vaccination and may also recommend an injection of hepatitis B immune globulin (HBIG). HBIG is prepared from the plasma of blood donors and contains antibodies to hepatitis B. Vaccination and HBIG can substantially reduce the risk of disease in persons exposed to hepatitis B if given within one week of a needle stick or two weeks of sexual intercourse.
Vaccination provides long-term immunity in people who respond to the vaccine. There is no need for HBIG if an exposure occurs to a vaccinated person who is known to have responded to the vaccine; however, a blood test might be drawn to verify that the person did respond to the vaccine and form antibodies.
Infected mothers can pass hepatitis B to their newborn infants. All pregnant women should have blood drawn to determine if they are infected. Infants born to infected mothers should receive HBIG and hepatitis B vaccine at birth. This is 85% to 95% effective in eliminating the risk of hepatitis B infection in the infant.
IMAGESSee a medical image of Hepatitis B along with other sexually transmitted diseases (STDs) See Images
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REFERENCE: Centers for Disease Control and Prevention. Hepatitis A Vaccine.
Centers for Disease Control and Prevention. Hepatitis B Vaccine.
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