Hepatitis B Vaccine Safe

by Food and Drug Administration (FDA)

Usually when a vaccine is found for a disease, the number of cases drops dramatically. But that hasn't happened with hepatitis B, a viral disease that attacks the liver.

According to the federal Centers for Disease Control, reported cases of acute hepatitis B continued to increase after the first vaccine was introduced in 1982 and reached a peak in 1985. CDC adds that even though the number of cases reported has decreased "modestly" since 1985, the number of new cases each year is still higher than before the vaccine was introduced. What happened?

Vaccination Strategy

Current public health efforts to prevent the disease have focused on vaccinating people in high-risk groups. Those at greatest risk are:

• intravenous (IV) drug abusers
• heterosexuals with multiple partners
• homosexual men

Other risk groups include:

• health-care workers
• children born to immigrants from China, Southeast Asia, and other areas where hepatitis B is very common.

This focus on high-risk groups has met with mixed success. In a New England Journal of Medicine editorial that appeared last November, Jay H. Hoofnagle, M.D., a researcher with the National Institutes of Health, explains that "Even in health care workers, the most easily reached and medically aware high-risk group, hepatitis B vaccination programs have not been completely successful: recent surveys show that less than 50 percent of the health care workers at high risk of contracting hepatitis B have received an adequate course of vaccination against the virus."

Even though fewer than half of health-care workers have been vaccinated, the number of cases of hepatitis B in that group dropped 75 percent between 1981 and 1988, according to a study by CDC published in the March 2 issue of the Journal of the American Medical Association. The study's authors, Miriam J. Alter, Ph.D., chief of epidemiology in CDC's hepatitis branch, and colleagues, say this drop is probably a direct result of immunization efforts and greater adherence to safe blood-handling procedures.

In addition to the drop in cases for health-care workers, the cases of hepatitis B have dropped 62 percent among homosexuals, "most likely as a result of a modification of high-risk behavior," according to the CDC study. But, during the same period, cases in IV drug abusers increased 80 percent.

Though these declines in cases are encouraging, vaccination efforts to reach some high-risk groups have been thwarted by the public's lack of knowledge about the disease's risks, the lack of government programs, the cost of the vaccine, and the inability to reach most of the high-risk populations, according to CDC.

Lack of knowledge is definitely part of the problem when it comes to health-care workers, says Jim Paturas, president of the National Association of Emergency Medical Technicians. According to a telephone survey last July commissioned by SmithKline Beecham, Philadelphia, which manufactures one of the hepatitis B vaccines, 26 percent of health-care workers don't think their jobs increase their risk of hepatitis B infection. Many health-care workers are "not in tune with the risk they are presented with daily," says Paturas. He adds that efforts to inform health-care workers about the risks of the disease must be increased.

Easier to Catch than AIDS

Although health-care workers and others at risk may not be getting — or may be ignoring — information geared to them about the dangers of hepatitis B, there is no lack of scientific information. How the hepatitis B virus is spread is fairly well understood.

Like AIDS, most cases can be traced to contact with infected blood, unprotected sexual intercourse, and needle-sharing among IV drug abusers. Infants born to infected mothers may be infected when they pass through the birth canal. Unlike AIDS, however, people living in the same household as an infected person are also at risk. Cuts, scrapes or other breaks in the skin can be an entry point for infected blood or other body fluids. According to CDC, this contact frequently may be "inapparent or unnoticed."

The chances of catching hepatitis B from blood transfusions is rare, however, because of routine blood screening for the hepatitis B surface antigen and current donor screening procedures, CDC says.

How contagious is the hepatitis B virus? According to CDC's Alter, a health-care worker who gets an accidental needle prick while treating patients infected with hepatitis B has between a 6 and 30 percent chance of becoming infected. By comparison, the chance of contracting AIDS from a needle prick is only about 0.5 percent, she says.

The symptoms of hepatitis B infection include vomiting, abdominal pain, loss of appetite, and jaundice (an excess of a bile pigment in the blood that causes the skin to look yellow). Nausea is usually not associated with hepatitis B; it is more common with hepatitis A (see accompanying article). Symptoms can appear anywhere from 45 to 160 days after exposure.

In approximately a third of all cases the infected individual does not develop the worst symptoms of the disease, but has only a mild flu-like illness without jaundice and then recovers. Another third develop no symptoms at all. But even those who don't suffer with the full-blown disease can become chronic carriers — that is, transmitters of the disease for the rest of their lives. In fact, the chances of becoming a carrier are greater if the symptoms don't develop.

In people who are first infected as adults, between 6 and 10 percent will continue to be contagious for the rest of their lives. However, up to half of children infected before their fifth birthday will become chronic carriers, and that figure jumps to 90 percent for babies infected at birth.

CDC estimates that approximately 25 percent of carriers do suffer chronic symptoms, and those people are at the greatest risk of one of the most serious consequences of infection, cirrhosis. A degenerative disease in which liver cells are damaged and replaced by scar tissue, cirrhosis caused by hepatitis B infections results in 4,000 deaths each year, according to CDC.

All carriers, whether or not they have active symptoms, have a 12 to 300 times greater risk of developing primary liver cancer than non-carriers. CDC estimates that more than 800 people die from hepatitis B-related liver cancer every year.

Modern Day Vaccine

The current vaccine, a genetically engineered product, has produced no known serious side effects and is effective between 80 and 95 percent of the time, according to CDC. The original plasma-derived vaccine, licensed in 1982, is no longer being manufactured. Because that vaccine was made from the plasma of chronic carriers of hepatitis B, many of whom are also at high risk for AIDS, there was concern that the vaccine might transmit the AIDS virus. However, a connection between AIDS transmission and the plasma-derived vaccine was "never shown," says FDA microbiologist Richard Daemer.

In 1987, FDA licensed the first genetically engineered hepatitis B vaccine — Recombivax HB, manufactured by Merck Sharp & Dohme, West Point, Pa. Two years later, the agency licensed SmithKline Beecham's Engerix-B, also manufactured by the same process of genetic engineering. Both are made by programming yeast cells to produce large quantities of a portion of the virus's outer coat, which stimulates protective antibody production. Unlike some other vaccines, there is no risk of serious side effects from the hepatitis B vaccine, according to Daemer. If there is any reaction at all, he says, it is "very minimal — maybe a sore arm [at the injection site] or a slight fever." The main reason for its safety, Daemer explains, is that the hepatitis B vaccine contains only a highly purified, incomplete virus particle. The whole virus is necessary to produce infection or serious reactions, while an incomplete virus simply provides immunity and "just can't do any damage, period," he says.

About the Author

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