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.
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. (Blumberg 2002) Vaccination is recommended for all those adults at high risk for exposure, such as health care workers, those with multiple sexual partners (both male and female), and sexual partners of those known to be infected. Although the risk is small, it is ongoing for those living in the same house with someone who has chronic hepatitis B, and vaccination is recommended for them as well. The American Academy of Pediatrics now strongly recommends that all children be vaccinated against hepatitis B, and the vaccine is being incorporated into the series of inoculations that children receive. (Blumberg 2000) Adolescents are also encouraged to receive the vaccine. Vaccines against both HAV and HBV can be effectively administered simultaneously. In most obstetrical units, mothers are tested for HBVsurface antigen during pregnancy or when they come in for delivery. (Lauffer et al 1993) Newborns of mothers who test positive are inoculated immediately after delivery with hyperimmune globulin to provide immediate protection and are simultaneously given the first shot of vaccine for long-term protection, since they are at high risk for developing chronic hepatitis B.