Hepatitis B is a more serious disease than hepatitis A because complications are more common. Some people become carriers of the virus with no symptoms or evidence of liver disease, while about 5 percent of exposed adults develop chronic hepatitis that can lead to cirrhosis and hepatocellular carcinoma. (Blumberg 2002) About 350 million people in the world are infected with the hepatitis B virus (HBV). The number who die each year with this infection approaches 1 million. Over half the population of Southeast Asia, China, and Africa are infected at some time in their lives, and 8 percent are chronic carriers. The carrier rate varies from less than 1 percent to as much as 20 percent of different populations of the world, with lowest rates in New Zealand, Australia, Western Europe, and North America. (Blumberg 2002) Some geographic or ethnic groups such as Alaskan Eskimos and Australian aborigines have higher prevalence of infection than other groups living in immediate proximity. African Americans and Hispanics have higher prevalence than others in the United States. A major problem in areas with high carrier rates is transmission from a mother who is a carrier to her infant.
These babies seldom have acute hepatitis, but about 90 percent become carriers of the disease and are able to transmit it to others. If the infection occurs later, between the ages of two to five years, the carrier rate is between 25 and 50 percent but only 5 percent thereafter. In the United States, some 98 percent of all babies born to mothers who are carriers are immediately immunized. Extrapolated data from population surveys suggest that about 5 percent of people in the United States have evidence of past exposure, the vast majority of whom are immune. Since 1985, the number of people who become infected annually has fallen by about 50 percent and is now estimated to be about forty per ten thousand. (Lauffer et al 1993) Obviously, avoiding behavior which puts a person at high risk for acquiring HBV is advisable. However, in a third of cases no such exposure has taken place (or is admitted to). For those who are known to have had recent exposure to a case of acute hepatitis, hyperimmune globulin against HBV, known as HBIG, is effective in preventing or meliorating the disease.
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Hyperimmune globulin contains high levels of antibodies against HBV, having been collected from persons who are specifically selected because of their high levels of HBV antibodies. (Lauffer et al 1993) “Not every person with chronic hepatitis B needs to be on medication.” (Hepatitis B Foundation) Vaccines have been developed that are highly effective in inducing antibodies against HBsAg and, therefore, in preventing the disease. The cost is about $150 for the recommended series of three injections. In the United States, the vaccine is available in local health department clinics at a reduced cost. Vaccines are made from purified surface antigen that is harvested from fungus in which the HBV surface antigen gene has been inserted. () The vaccine contains only the surface antigen and no part of the virus. It cannot transmit the disease. It is given by injection in three doses over a period of six months and induces antibodies in about 90 percent of people. (Lauffer et al 1993) Since surface protein is essential for virus survival, antibodies destroy the virus before it becomes attached to the hepatic cell and causes infection. Those who are obese have a lower response rate than those of normal body weight, presumably because the vaccine is ineffectively absorbed from fatty tissue where it is injected. If those who do not develop antibodies undergo another series of injections, only about 10 percent will convert to an immune state. Interestingly, there is some evidence that those who receive the vaccine but do not develop antibodies are nevertheless partially protected when exposed. The level of antibodies reaches a peak shortly after the second or third injection, and the antibodies persist for years with a slow reduction in measurable levels. By the tenth year, the levels are low or undetectable, and a booster shot every ten years is recommended by some. A normal trait of the immune system that has previously produced antibodies to an antigen is to retain the memory of how to do it—it does not have to relearn. Thus, reexposure to an antigen, such as that of HBV, results in an immediate outpouring of antibodies even when there are no measurable levels before exposure. This is called the “anamnestic” response.
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