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Hepatitis B
 
 
  The term 'hepatitis' simply means inflammation of the liver. Hepatitis may be caused by a virus or a toxin such as alcohol. Other viruses that can cause injury to liver cells include the hepatitis A and hepatitis C viruses. These viruses are not related to each other or to hepatitis B virus and differ in their structure, the ways they are spread among individuals, the severity of symptoms they can cause, the way they are treated, and the outcome of the infection.




Hepatitis B is an infection of the liver caused by the hepatitis B virus (HBV). It is estimated that 350 million individuals worldwide are infected with the virus, which causes 620,000 deaths worldwide each year. According to the Centers for Disease Control (CDC), approximately 46,000 new cases of hepatitis B occurred in the United States in 2006.

In the United States, rates of new infection were highest among people aged 25 to 44 years (3.1 cases per 100,000 population) and lowest among those younger than 15 years of age (0.02 per 100,000). This reflects the major modes of transmission of hepatitis B (sexual transmission, illicit drug use, exposure to infected blood) and the effect of universal vaccination of infants. In the United States, there has been a 75% decrease in newly diagnosed cases of hepatitis B during the past decade. This decrease is attributed to increased vaccination and to heightened public awareness of HIV/AIDS and the resulting safer sexual practices.

When a person first gets hepatitis B, they are said to have an 'acute' infection. Most people are able to eliminate the virus and are cured of the infection. Some are not able to clear the virus and have 'chronic' infection with hepatitis B that is usually life-long (see below). In the United States an estimated 800,000 to 1.4 million people are chronically infected with hepatitis B.

Hepatitis B is found throughout the world. Some countries have much higher rates of infection than the United States; for example, in Southeast Asia and Sub-Saharan Africa, as many as 15% to 20% of adults are chronically infected with hepatitis B.

What kind of a virus is hepatitis B?

The hepatitis B virus is a DNA virus, meaning that its genetic material is made up of deoxyribonucleic acids. It belongs to a family of viruses known as Hepadnaviridae. The virus is primarily found in the liver but is also present in the blood and certain body fluids.

Hepatitis B virus consists of a core particle (central portion) and a surrounding envelope (outer coat). The core is made up of DNA and the core antigen (HBcAg). The envelope contains the surface antigen (HBsAg). These antigens are present in the blood and are markers that are used in the diagnosis and evaluation of patients with suspected viral hepatitis.

How does hepatitis B virus cause liver injury?

The hepatitis B virus reproduces in liver cells, but the virus itself is not the direct cause of damage to the liver. Rather, the presence of the virus triggers an immune response from the body as the body tries to eliminate the virus and recover from the infection. This immune response causes inflammation and may seriously injure liver calls. Therefore, there is a balance between the protective and destructive effects of the immune response to the hepatitis B virus.
How is the hepatitis B virus spread (transmitted)?

Hepatitis B is spread mainly by exposure to infected blood or body secretions. In infected individuals, the virus can be found in the blood, semen, vaginal discharge, breast milk, and saliva. Hepatitis B is not spread through food, water, or by casual contact.

In the United States, sexual contact is the most common means of transmission, followed by using contaminated needles for injecting illicit drugs, tattooing, body piercing, or acupuncture. Additionally, hepatitis B can be transmitted through sharing toothbrushes and razors contaminated with infected fluids or blood.

Hepatitis B also may be spread from infected mothers to their babies at birth (so-called 'vertical' transmission). This is the most prevalent means of transmission in regions of the world where hepatitis B rates are high. The rate of transmission of hepatitis B from mother to newborn is very high, and almost all infected infants will develop chronic hepatitis B. Fortunately, transmission can be significantly reduced through immunoprophylaxis (see below).

Rarely, hepatitis B can be transmitted through transfused blood products, donated livers and other organs. However, blood and organ donors are routinely screened for hepatitis which typically prevents this type of transmission.


What are the symptoms of acute hepatitis B?

Acute hepatitis B is the period of illness that occurs during the first one to four months after acquiring the virus. Only 30% to 50% of adults develop significant symptoms during acute infection. Early symptoms may be non-specific, including fever, a flu-like illness, and joint pains. Symptoms of acute hepatitis may include:

fatigue,


loss of appetite,


nausea,


jaundice (yellowing of the skin and eyes), and


pain in the upper right abdomen (due to the inflamed liver).
Rarely, acute hepatitis damages the liver so badly it can no longer function. This life-threatening condition is called "fulminant hepatitis." Patients with fulminant hepatitis are at risk of developing bleeding problems and coma resulting from the failure of the liver. Patients with fulminant hepatitis should be evaluated for liver transplantation. Small studies suggest that the drug lamivudine (Epivir), may be of limited assistance in these cases (see below).

What determines the outcome of acute hepatitis B?

The body's immune response is the major determinant of the outcome in acute hepatitis B. Individuals who develop a strong immune response to the infection are more likely to clear the virus and recover. However, these patients also are more likely to develop more severe liver injury and symptoms due to the strong immune response that is trying to eliminate the virus. On the other hand, a weaker immune response results in less liver injury and fewer symptoms but a higher risk of developing chronic hepatitis B. People who recover and eliminate the virus will develop life-long immunity, that is, protection from subsequent infection from hepatitis B.

Most infants and children who acquire acute hepatitis B viral infection have no symptoms. In these individuals, the immune system fails to mount a vigorous response to the virus. Consequently, the risk of an infected infant developing chronic hepatitis B is greater than 95%. In contrast, only 5% of adults who have acute hepatitis B develop chronic hepatitis B.

What are the symptoms of chronic hepatitis B?

The liver is a vital organ that has many functions. These include a role in the immune system, production of clotting factors, producing bile for digestion, and breaking down toxic substances, etc. Patients with chronic hepatitis B develop symptoms in proportion to the degree of abnormalities in these functions. The signs and symptoms of chronic hepatitis B vary widely depending on the severity of the liver damage. They range from few and relatively mild signs and symptoms to signs and symptoms of severe liver disease such as cirrhosis or liver failure.

Most individuals with chronic hepatitis B remain symptom free for many years or decades. During this time, the patient's blood tests usually are normal or only mildly abnormal. Some patients may deteriorate and develop inflammation or symptoms, putting them at risk for developing cirrhosis.

Cirrhosis of the liver due to hepatitis B

Inflammation from chronic hepatitis B can progress to cirrhosis (severe scarring) of the liver. Significant amounts of scarring and cirrhosis lead to liver dysfunction.

Symptoms may include:

weakness,


fatigue,


loss of appetite,


weight loss,


breast enlargement in men,


a rash on the palms,


difficulty with blood clotting, and


spider-like blood vessels on the skin.
Decreased absorption of vitamins A and D can cause impaired vision at night and thinning of bones (osteoporosis). Patients with liver cirrhosis also are at risk of infections because the liver plays an important role in the immune system.

Advanced cirrhosis of the liver due to hepatitis B

In patients with advanced cirrhosis, the liver begins to fail. This is life-threatening condition.

Several complications occur in advanced cirrhosis:

Confusion and even coma (encephalopathy) results from the inability of the liver to detoxify certain toxic substances.


Increased pressure in the blood vessels of the liver (portal hypertension) causes fluid to build up in the abdominal cavity (ascites) and may result in engorged veins in the swallowing tube (esophageal varices) that tear easily and may cause massive bleeding.


Portal hypertension can also cause kidney failure or an enlarged spleen resulting in a decrease of blood cells and the development of anemia, increased risk of infection and bleeding.


In advanced cirrhosis, liver failure also results in decreased production of clotting factors. This causes abnormalities in blood clotting and sometimes spontaneous bleeding.


Patients with advanced cirrhosis often develop jaundice because the damaged liver is unable to eliminate a yellow compound, called bilirubin.
Hepatitis B virus and primary liver cancer (hepatocellular carcinoma)

Patients with chronic hepatitis B are at risk of developing liver cancer. The way in which the cancer develops is not fully understood. Symptoms of liver cancer are nonspecific. Patients may have no symptoms, or they may experience abdominal pain and swelling, an enlarged liver, weight loss, and fever. The most useful diagnostic screening tests for liver cancer are a blood test for a protein produced by the cancer called alpha-fetoprotein and an ultrasound imaging study of the liver. These two tests are used to screen patients with chronic hepatitis B, especially if they have cirrhosis or a family history of liver cancer.

Hepatitis B virus involvement of organs outside of the liver (extra-hepatic)

Rarely, chronic hepatitis B infection can lead to disorders that affect organs other than the liver. These conditions are caused when the normal immune response to hepatitis B mistakenly attacks uninfected organs.

Among these conditions are:

Polyarteritis nodosa: a disease characterized by inflammation of the small blood vessels throughout the body. This condition can cause a wide range of symptoms, including muscle weakness, nerve damage, deep skin ulcers, kidney problems, high blood pressure, unexplained fevers, and abdominal pain.


Glomerulonephritis: another rare condition, which is inflammation of the small filtering units of the kidney.

How is hepatitis B diagnosed?

Infection with hepatitis B is suspected when the medical history and the physical examination reveal risk factors for the infection or symptoms and signs that are suggestive of hepatitis B. Abnormalities in the liver tests (blood tests) also can raise suspicion; however, abnormal liver tests can result from many conditions that affect the liver. The diagnosis of hepatitis B can be made only with specific hepatitis B virus blood tests. These tests are known as hepatitis 'markers' or 'serology.'

Markers found in the blood can confirm hepatitis B infection and differentiate acute from chronic infection. These markers are substances produced by the hepatitis B virus (antigens) and antibodies produced by the immune system to fight the virus. Hepatitis B virus has three antigens for which there are commonly-used tests - the surface antigen (HBsAg), the core antigen (HBcAg) and the e antigen (HBeAg).

HBsAg and anti-HBs

The presence of hepatitis B surface antigen (HBsAg) in the blood indicates that the patient is currently infected with the virus. HBsAg appears an average of four weeks after initial exposure to the virus. Individuals who recover from acute hepatitis B infections clear the blood of HBsAg within approximately four months after the onset of symptoms. These individuals develop antibodies to HBsAg (anti-HBs). Anti-HBs provides complete immunity to subsequent hepatitis B viral infection. Similarly, individuals who are successfully vaccinated against hepatitis B produce anti-HBs in the blood.

Patients who fail to clear the virus during an acute episode develop chronic hepatitis B. The diagnosis of chronic hepatitis B is made when the HBsAg is present in the blood for at least six months. In chronic hepatitis B, HBsAg can be detected for many years, and anti-HBs does not appear.

Anti-HBc

In acute hepatitis, a specific class of early antibodies (IgM) appears that is directed against the hepatitis B core antigen (anti-HBc IgM). Later, another class of antibody, anti-HBc IgG, develops and persists for life, regardless of whether the individual recovers or develops chronic infection. Only anti-HBc IgM can be used to diagnose an acute hepatitis B infection.

HBeAg, anti-HBe, and pre-core mutations

Hepatitis B e antigen (HBeAg) is present when the hepatitis B virus is actively multiplying, whereas the production of the antibody, anti-HBe, (also called HBeAg seroconversion) signifies a more inactive state of the virus and a lower risk of transmission.

In some individuals infected with hepatitis B virus, the genetic material for the virus has undergone a structural change, called a pre-core mutation. This mutation results in an inability of the hepatitis B virus to produce HBeAg, even though the virus is actively reproducing. This means that even though no HBeAg is detected in the blood of people with the mutation, the hepatitis B virus is still active in these persons and they can infect others.

Hepatitis B virus DNA

The best marker of hepatitis B virus reproduction is the level of hepatitis B virus DNA in the blood. Detection of hepatitis B virus DNA in a blood sample signals that the virus is actively multiplying. In acute hepatitis, HBV DNA is present soon after infection, but is eliminated over time in patients' who clear the infection. In chronic hepatitis, levels of HBV DNA often continue to be elevated for many years and then decrease as the immune system controls the virus. HBV DNA levels are sometimes referred to as the 'viral load'.  

  
 What is the role of a liver biopsy in chronic hepatitis B?

During a liver biopsy, a small sample of liver tissue is collected and examined under the microscope. This test is valuable because this sample reflects the health of the liver. It can show the amount of liver injury (inflammation or cirrhosis). Liver biopsy is not routinely needed to diagnose hepatitis B, but it is used for monitoring the progression of liver damage in people with chronic hepatitis and helping to choose or evaluate treatment options.


What is the natural course of chronic hepatitis B?

The course of chronic hepatitis B is variable and depends on several factors. These factors are the patient's age at which the infection began, the extent of viral multiplication, and the immune system's ability to control the infection.

The infection can progress from an:

immune tolerant phase (in which the immune system ignores the virus)


immune clearance phase (in which the immune system attempts to eliminate the virus)


quiescent phase (in which the virus is less active)
Immune tolerant phase

For individuals infected at birth or at a young age, the immune system initially does not react to the hepatitis B virus. This phase of the infection is known as the immune tolerant phase. Despite high levels of virus in the body, there may be little evidence of inflammation and no symptoms. This phase typically lasts for years, even up to two or three decades. It is important to know that the immune tolerant phase is generally not seen in individuals who become infected during adulthood.

Immune clearance phase

During the third to fourth decade of chronic hepatitis B acquired in childhood, the immune system may start to react to the virus. This is known as the immune clearance phase. In contrast, an infection acquired in adulthood usually begins with the immune clearance phase. In the immune clearance phase, the immune system attacks the hepatitis B virus-infected liver cells in an attempt to clear the virus. This causes inflammation, liver injury, and the development of scar tissue. Standard liver blood tests are abnormal, and the liver biopsy shows inflammation and/or formation of scar tissue (fibrosis). The severity of liver cell destruction, the degree of fibrosis, and the duration of the immune clearance phase determine the outcome of chronic hepatitis B. The more severe the destruction and fibrosis and the longer the phase, the more likely it is that cirrhosis will develop.

Quiescent phase

Following the immune clearance phase, the viral infection may enter a less active phase known as the quiescent phase. During this phase, there are no symptoms, the levels of hepatitis B virus become very low, and the standard liver blood tests become normal or nearly normal. Advanced scaring or cirrhosis that may have developed earlier, however, remains. Occasionally, during the quiescent phase, the virus becomes active again. This is known as a "flare," and often is associated with symptoms, abnormal liver blood tests, and further injury to the liver. The flares are caused by reactivation of the immune system against the virus. Flares can be very severe and result in further scarring of the liver. The disease in many of these individuals will progress to cirrhosis and eventually to advanced or end-stage cirrhosis with its associated complications, including liver cancer.

Infected individuals who experience a mild immune clearance phase and move into the quiescent phase are known as healthy carriers of hepatitis B virus. These individuals usually have normal liver tests and do not have symptoms; however, they can still transmit the hepatitis B viral infection to others. The risk of hepatitis B virus carriers developing cirrhosis and liver cell cancer is small although the risk is higher as compared to people without chronic hepatitis B.

What medications are used to treat hepatitis B?

Acute infection

Acute infection with hepatitis B usually does not require treatment. In rare cases, however, the infection may cause life-threatening liver failure. Patients with liver failure due to acute hepatitis B should be evaluated for liver transplantation. Small studies suggest that the drug lamivudine (Epivir) may be effective in this setting.

Chronic infection

If a person is chronically infected with hepatitis B and has few signs or symptoms of complications, medications usually are not used. These patients are watched carefully and given periodic blood tests. One test measures the 'viral load,' that is, the amount of viral DNA in the blood. Doctors will recommend treatment if there are signs that the virus is beginning to cause damage or if the viral load is high. Another reason to prescribe medication is if the patient has a positive test for the Hepatitis B e-antigen (HBeAg) in the blood. HBeAg is associated with an increased risk of progression of liver disease and its complications.

In chronic hepatitis B, the goal of treatment is to reduce the risk of complications including cirrhosis and liver failure. However, it takes decades for complications to occur, which makes it difficult to study the effect of medications. As a substitute for waiting years to find out what happens, scientists have used tests like the viral load or liver function tests to evaluate if medicines are working. This is logical because it is known that people who have large amounts of the virus in their blood are at highest risk to get cirrhosis. Up to one-third of people with very high viral loads (more than one million viral copies per milliliter of blood) will develop cirrhosis over a decade, compared to only 4.5% of those with low viral loads (fewer than 300 viral copies per milliliter).

Medications can reduce the number of viruses in the body and may be able to eliminate the virus from the bloodstream. Logically, this should lead to them having a low rate of progression to cirrhosis (<1% per year), although large, long-term studies have not been done. Even in people who clear the virus from their blood, low numbers of viruses still live in the liver and other cells. Thus, the medications do not cure the disease, but they can prevent or delay complications and symptoms. People who have a good response to treatment can still transmit the virus. Doctors follow blood tests that measure viral load and liver function and they may recommend liver biopsies to evaluate if the medications are working.

The medications in current use for chronic hepatitis B include the interferons and nucleoside/nucleotide analogues. New agents are being developed although they are still under investigation and considered experimental. There are no accepted guidelines that tell how every patient should be treated. As a result, treatment is individualized.

Interferon

Interferon-alpha has been used to treat hepatitis B for more than 20 years. Interferon-alpha is a naturally occurring protein that is made in the body by white blood cells to combat viral infections. In addition to its direct anti-viral effects, interferon works against the hepatitis B virus by stimulating the body's immune system to clear the virus. Compared to older interferon alpha agents, pegylated interferon alpha, marketed as Pegasys or Pegintron, has a more convenient dosing schedule, may be slightly more effective and suppresses the virus for a longer period of time. Pegylated interferon alpha is given once a week for 48 weeks.

A significant reduction in the viral load or elimination of detectable viral DNA from the blood occurs in two-thirds of persons during treatment.


Blood tests for liver functions normalize in approximately 40% people treated with interferon.


People who have significant abnormalities in liver function before therapy are more likely to respond to treatment.


Those who have normal liver blood tests before treatment are less likely to respond to interferon therapy.


Liver biopsy results show improvement in about one-third of patients.
Only 27%-32% of persons who have Hepatitis B e-antigen (HBeAg) in their blood will be able to eliminate HBeAg and produce antibodies against the HBe antigen after treatment with interferon. Relapse may occur after treatment is stopped.

Sustained response (undetectable viral load in the blood, normal liver function tests) occurs in approximately 15% to 30% of patients after the drug is stopped. Although this is not a cure (some virus still lives in the liver and elsewhere), people with sustained response are at low risk for complications of liver disease. If the responder's immune system is compromised, for example through the use of steroids or acquiring HIV, the disease can recur. Periodic monitoring of blood tests can help confirm that the response continues to be sustained.

Interferon side effects

Interferon causes several side effects including:

fatigue, generalized muscle aches, fever, chills and loss of appetite. These flu-like symptoms occur in approximately 80% of treated patients;


mood swings, depression, anxiety and other neuropsychiatric effects may occur; and


thyroid gland abnormalities resulting in hypothyroidism (too little thyroid hormone);


significant suppression of the bone marrow and production of blood cells;


infection;


or hair loss may occur.
The side effects may be severe enough that the patient is unable to continue treatment. During treatment, the normal immune response to the virus is stimulated and may cause worsening inflammation in the liver. This is normally a good sign showing that the interferon is working, but more extreme responses may in rare cases cause liver failure. Thus, physicians will monitor blood tests closely during therapy. Persons with unstable liver disease due to cirrhosis usually should not take interferon because of the increased risk of liver failure.

Nucleoside/nucleotide analogues

Nucleoside/nucleotide analogues (NAs) are man-made chemicals that mimic the nucleosides and nucleotides that are used for making DNA. When the virus tries to use the analogues to make its own DNA, it is unable to make the DNA and, therefore, cannot reproduce. Examples of these agents include adefovir (Hepsera), entecavir (Baraclude), lamivudine (Epivir-HBV, Heptovir, Heptodin), telbivudine (Tyzeka) and tenofovir (Viread).

In patients who have HBeAg in their blood, NAs reduce the viral load, causing the virus to become undetectable in 21% to 67% of patients.


Normalization of blood liver tests occurs in 40% to 77%, and loss of HBeAg occurs in approximately 12% to 22% of cases after one year of treatment.


Results are better in patients who do not have HBeAg in their blood, with 50% to 90% having non-detectable virus and 60% to 80% having normalization of liver function tests.
In a 2004 study in people who already had cirrhosis from hepatitis B, treatment with lamivudine cut the risk of liver cancer and progressive liver failure by more than 50%. Newer NAs such as entecavir (Baraclude) and telbivudine (Tyzeka) appear to have higher response rates than older agents such as lamivudine (Epivir-HBV, Heptovir, Heptodin), but there is less experience with these NAs.

Unfortunately, the hepatitis B virus may become resistant to NAs over time (see below). Adefovir may be effective against strains of virus that have become resistant to lamivudine and may be added to lamivudine when resistance appears. Simply switching from one NA to another is not recommended because this leads to virus strains that are resistant to multiple medications.

Currently, the optimal duration of treatment with nucleoside/nucleotide analogues is uncertain. Persons with HBeAg may be treated until six months after the HBeAg disappears from the blood and is replaced by antibodies (anti-HBe), if this occurs. In persons without HBeAg, the endpoints are less clear. Some experts advocate treating until the viral load (viral DNA) is undetectable and the surface antigen (HbsAg) has been cleared from the blood. Others suggest continuing medications for prolonged periods to suppress the virus. All of these strategies are hampered by the risk of the virus becoming resistant to the medications. Patients who discontinue treatment with NAs should be monitored carefully for recurrent hepatitis, which may be severe.

Why does hepatitis B virus become resistant to nucleoside/nucleotide analogues?

The major challenge associated with long-term therapy with NAs is the development of viral resistance to the NAs. This resistance results from a change (mutation) in the genetic material of the virus.

For lamivudine (Epivir-HBV, Heptovir, Heptodin), the incidence of resistance is 25% after one year and as high as 50% after three years of treatment.


With telbivudine (Tyzeka), resistance rates are 5% to 11% after one year.
Therefore, some guidelines do not recommended lamivudine or telbivudine alone as the first treatment for chronic hepatitis B.

For other NAs such as adefovir (Hepsera), resistance is less common after one year of therapy but rises to 30% after five years. Early results with entecavir (Baraclude) suggest that resistance may be uncommon with this agent. When resistance occurs, the viral load may rise or blood liver tests may become abnormal.

Is there a preferred treatment for chronic hepatitis B?

There are no clear guidelines to recommend which agent to use first in treating chronic hepatitis B. Interferon is given for a defined period of time and may have a more prolonged response after the medication is discontinued than NAs. However, interferon is given as an injection, and side effects often are troublesome. NAs are given as a pill and have few side effects, but the duration of treatment is unclear, and prolonged therapy may be required. NAs may be preferred in patients with unstable disease and cirrhosis because they are thought to be less likely to cause serious flares of hepatitis with more severe liver disease.

What are the effects of alcohol on hepatitis B virus?

Agents that damage the liver are particularly harmful in patients who already have hepatitis B. For this reason, it is recommended that persons with hepatitis B avoid drinking alcohol.


What are the effects of immunosuppressive medications on hepatitis B virus?

Even in people with chronic hepatitis B, the immune system is working to suppress the virus. Medications that suppress the immune system allow the virus to reproduce in large numbers and may cause the hepatitis to flare.

Examples of medications that suppress the immune system are:

prednisone: used to treat many diseases, including asthma, inflammatory bowel disease, and certain types of skin disease and arthritis


methotrexate (Rheumatrex, Trexall): used to treat certain types of skin disease, arthritis, and cancer;


cyclophosphamide (Cytoxan): used to treat some cancers.
If an immunosuppressant drug is stopped, the body's immune system's activity may rebound and cause severe inflammation of the liver.


What is delta hepatitis?

Delta hepatitis is caused by a virus that only infects people who already have hepatitis B. The delta hepatitis virus (also known as hepatitis D or HDV) is an RNA virus, meaning that its genetic material is made up of ribonucleic acid. It is spread through exposure to contaminated blood, especially with illicit, intravenous drug use, and by sexual contact. Delta hepatitis can be acquired at the same time as acute hepatitis B. When this happens, infected people are quite sick but more than 95% are eventually able to eliminate the viruses from their bodies. People who already have chronic hepatitis B can acquire delta hepatitis as well. This often causes severe inflammation of the liver, and the viruses are less likely to be cleared.

Delta hepatitis makes chronic hepatitis B much worse. It increases the risk of complications, especially cirrhosis, which occurs in up to two-thirds of patients.

There is no vaccine against delta hepatitis. Interferon treatment may cause improvement in the hepatitis, but relapse is common after therapy is stopped. Prevention includes avoiding contaminated needles and practicing safer sex (abstaining or limiting the number of partners, using barrier methods of contraception). Universal vaccination of newborns with hepatitis B vaccine effectively prevents delta hepatitis because the delta hepatitis virus only causes disease in the presence of hepatitis B virus.

What can be done to prevent hepatitis B?

Hepatitis B is a preventable disease. Vaccination and post-exposure prophylaxis have significantly reduced rates of infection. Risk can also be reduced by avoiding unprotected sex, contaminated needles, and other sources of infection.

How effective is vaccination for hepatitis B?

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, 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.

Examples include:

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).


Pediarix provides protection against hepatitis B, tetanus, pertussis (whooping cough), and polio.
Hepatitis B vaccines are effective and safe. Up to 95% of vaccinated individuals form effective antibodies when they get the vaccine and are protected from hepatitis B. In healthcare workers, high-risk public safety workers, dialysis patients, and sexual partners of infected persons, a blood test for antibodies is recommended after vaccination to ensure that the person produced antibodies. For the few who do not form antibodies, revaccination may improve response, especially in infants. However, a small proportion of individuals will never respond to hepatitis B vaccination. Side effects from the vaccine are usually mild and include soreness at the site of injection. The risk of serious allergic reactions (anaphylaxis) is less than one per million doses. Vaccination has reduced the number of new cases of hepatitis B by more than 75% in the United States.

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 do so at birth.

Adults in high risk situations also are advised to receive hepatitis B vaccine. This includes:

health care workers


dentists


intimate and household contacts of patients with chronic hepatitis B infection


public safety workers who may be exposed to blood


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 HIV


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. Some countries have a high prevalence of hepatitis B in their population. Travelers who visit these countries for a prolonged period of time (usually six months) and those who may be exposed to blood or semen should consider vaccination.

How effective is hepatitis B immune globulin (HBIG) in preventing hepatitis B?

HBIG is a product that contains antibodies against hepatitis B. When injected, it provides temporary protection against hepatitis B. HBIG is used when people have had significant exposure to the virus. An example would be an accidental needle stick in an unvaccinated health care worker from a needle contaminated with blood from a person with hepatitis B. HBIG should be given as soon as possible after exposure, preferably within seven days. Persons who need HBIG should also receive hepatitis B vaccine. HBIG also is given to patients with hepatitis B following liver transplantation to suppress the hepatitis B virus in the transplanted liver.

What is post-exposure immunoprophylaxis for hepatitis B virus?

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 also may 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 respond to the vaccine; however, a blood test might be drawn to verify that the person did respond to the vaccine.

How is transmission of hepatitis B virus from mother to newborn infant prevented?

Infected mothers can pass hepatitis B to their newborn infants. All pregnant women should have blood tested 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 in the infant.