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Monday, November 16, 2009
Shingles vaccine battles pre-existing infection, can reduce severity
By Matt Andazola
Journal Staff Writer
Shingles is infamous for its associated rashes and sometimes debilitating pain, but even the experts are stumped by the details of who gets it and why.
Doctors do know that a vaccine created in the past 10 years will cut the number of patients with the condition in half and reduce by 67 percent the chance of lingering pain afterward.
"From a physician's viewpoint, it's 10 times better to prevent the infection than it is to try to treat it," says Dr. Larry Davis, chief of the neurology service at the Department of Veterans Affairs medical center in Albuquerque. "There's no question about that. Even though there are antiviral drugs for this infection, they only help a little bit."
But he says the vaccine works differently from any other.
"It's the first time that a vaccine worked by boosting your immunity to a pre-existing infection," Davis says.
Between 90 percent and 100 percent of adults have the herpes zoster virus, which causes chickenpox. He says that until a vaccine became widespread in the mid-'90s, the vast majority of people caught chickenpox when they were children, resulting in an illness that could be very mild (one or two bumps and it's over) or very serious (high fever, severe rashes that last for weeks).
When someone has chickenpox, Davis says, the body's immune system beats back the infection, but some viruses take refuge inside nerve cells. There they remain, dormant, waiting for the opportunity to re-emerge as shingles.
Doctors don't know for sure if the virus changes with age, Davis says, and there doesn't seem to be a significant difference between the immune systems of those who get shingles and those who don't.
He says the illness is more common with age and those who are under a lot of stress, including those with AIDS or cancer.
When people do get shingles, says Dr. John Liljestrand of Presbyterian Medical Group, it can be a "painful, prolonged illness," the main feature of which is a rash of blisters that covers some portion of one side of a patient's body. Severe rashes can be debilitating.
The initial emergence of shingles can last months, but Liljestrand says the illness's most feared complication is postherpetic neuralgia — pain that lingers after the rash subsides — affecting about 2 percent of shingles patients.
"It can be very severe chronic pain," he says, adding that he treats about a dozen patients who have had postherpetic neuralgia for up to 15 years. "They just kind of have to live with that."
Chickenpox roots
The shingles vaccine first came about, Davis says, when the chickenpox vaccine was shown to be effective in children.
Because the researchers knew there was no difference in the immune systems of those who do or don't get shingles, they decided to engage the cellular systems that detect and kill viruses using different mechanisms from the antibodies that usually stave off invading elements.
Using a modified chickenpox vaccine in the late '90s, researchers with the pharmaceutical company Merck entered into a massive clinical trial in partnership with the Department of Veterans Affairs, testing more than 38,000 men and women nationwide.
Davis, who helped carry out the study in Albuquerque, says the only requirement for subjects was that they were healthy and older than 60 (an arbitrary age, Davis says, meant to recognize that seniors are more likely to get the illness than others).
In the double-blind study, doctors gave each patient the vaccine or a placebo, then monitored them for an average of three years.
One of the participants was Kathryn Jones, 88, of Albuquerque, who says she participates in many age-related studies but that the shingles study was important to her.
"I had known people that had had it, and I knew how terrible it was and could be," she says. "I felt that it was such a great need."
According to the New England Journal of Medicine, where the study was originally published, 1,000 of the participants — including Jones — eventually showed signs of shingles.
"It was uncomfortable; I had a very light case," she says. "I was fortunate that it wasn't the kind that lasts for months."
Davis and the other researchers found that those who received the vaccine were half as likely to have shingles as those who did not. Jones was part of the control group who received only the placebo.
Testing also showed that none of the shingles cases had been caused by the virus in the vaccine, but were the result of the wild virus reactivating.
Perhaps the most notable findings of the study were those showing that, of those who had shingles, the participants in the control group were nearly three times as likely to have postherpetic neuralgia.
Side effects of the vaccine were typical of those of other shots like the seasonal flu, including irritation near the site of the shot.
Speedy approval
Based on the size of the study and the clarity of its findings, Davis says the Food and Drug Administration approved the Zostavax vaccine much faster than usual for a new drug.
The Centers for Disease Control and Prevention recommends the shot for everyone age 60 and older, because that was the cutoff point used in the study.
The vaccine has some limitations; Davis says it must be kept at about 70 degrees below zero to be viable, and freezers that go that low in temperature are much more common in pediatricians' offices to house the similar chickenpox vaccine.
A new variety of Zostavax, stored at a more forgiving 20 degrees below zero, is being tested.
Also, because current government guidelines are based on the original study, variations of the vaccine are being tested on younger age groups and on those with other conditions that can leave them open to shingles.
Get vaccinated
The Centers for Disease Control and Prevention recommends everyone over age 60 receive the shingles vaccine once. If you've had shingles, getting the vaccine could further lower the chances of another outbreak.
Dr. John Liljestrand says many insurers cover the shingles vaccine, which can cost as much as $300 without insurance.
Tony Salters, a spokesman for the national Centers for Medicare and Medicaid Services, writes in an e-mail that the shingles vaccine is covered under Medicare Part D.
Those covered under a Part D plan should contact the drug or health plan in advance to see which doctors or pharmacies can be used to receive the vaccine at the plan's regular copay.
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