Shingles: Prevention

by Food and Drug Administration (FDA)

(Page 3 of 3)

Prevention, Almost Perfect

Before the FDA approved the chickenpox vaccine in 1995, about 95 percent of the U.S. population developed chickenpox before age 18. Since then, more than 60 percent of American youngsters have been vaccinated against chickenpox.

"The vaccine is a live attenuated strain of the chickenpox virus," says Philip R. Krause, M.D., lead research investigator in the FDA's Center for Biologics Evaluation and Research. "However, it's a weaker form so it gives rise to a milder infection. But in the course of giving rise to this milder infection, it induces enough immunity to prevent people from getting the natural infection." It is estimated that the vaccine is between 75 and 85 percent effective in preventing chickenpox. "But the important thing," says Krause, "is that it is almost completely effective in preventing severe cases of chickenpox."

Now that we have a chickenpox vaccine, are shingles and PHN on their way out? Although the FDA hasn't evaluated the effects of the vaccine on shingles, Krause believes that "in the long term, if you can prevent enough people from getting the wild (natural) type of chickenpox, you're likely to see a beneficial effect on the incidence of shingles and post-herpetic neuralgia. But it may take several generations for this to happen."

People who have had chickenpox (varicella zoster) in their youth can develop shingles (herpes zoster) in later years. During an acute attack of the chickenpox virus, most of the viral organisms are destroyed, but some survive, travel up nerve fibers along the spine, and lodge in nerve cells where they may lie dormant for many years. A decrease in the body's resistance can cause the virus to reawaken decades later. It then travels back down the nerve fibers to the skin's surface.

The reawakened virus generally causes a vague burning sensation or tingling over an area of skin. A painful rash usually occurs two to five days after the first symptoms appear. A cluster of small bumps (1) turns into blisters (2) that resemble chickenpox lesions. The blisters fill with pus, break open (3), crust over (4), and finally disappear. This process takes four to five weeks.

A painful condition called post-herpetic neuralgia can sometimes occur. This condition is thought to be caused by damage to the nerves (5), and can last from weeks to years after the rash disappears.

Shingles Prevention Study

For many years, physicians could shorten the episodes of shingles, but they have had no means to prevent the disease, which affects up to one-half of all people who reach the age of 85. Now, this void in the medical armamentarium may change as a result of a major study of an experimental vaccine conducted by the Department of Veterans Affairs in collaboration with the National Institute of Allergy and Infectious Diseases (NIAID) and Merck & Co.

The study, whose outcome was announced in June, 2005, was launched in 1999 and included 38,546 participants 60 years of age or older. The volunteers' average age was 69, 7 percent were older than 80, and 40 percent were women. Half of the subjects were injected with a highly potent version of VZV, Merck's chickenpox vaccine for immunization of children, and half received a placebo.

By the end of the randomized, double-blind trial, 642 (3.3 percent) of the placebo recipients but only 315 (1.6 percent) of those treated with vaccine were diagnosed with shingles. The difference in the incidence of postherpetic neuralgia was even greater: the painful condition affected 80 study subjects on placebo, but only 27 of those who had been vaccinated.

"A preventive shingle vaccine would be an enormous boon for the health and quality of life of seniors," said Anthony S. Fauci, M.D., director of the NIAID. "We are extremely gratified that the public-private partnership has led to these exciting results, which have the potential to greatly benefit seniors in years to come."

About the Author

www.fda.gov
FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.