Having shingles can be a miserable experience. Now, to make matters worse, the long-held notion that people can only get shingles once in their lives appears to be false, according to a study in the journal Mayo Clinic Proceedings this month.
It's estimated that 1 in 3 Americans will get shingles at some point, with one million new cases reported a year in the U.S. It typically starts with itching, tingling or numbness, then develops into a painful rash that blisters. It often hits people who are elderly or already suffering from another illness or trauma, and the residual nerve pain can last for months.
The incidence rate has been rising around the world, in all age groups, though it isn't clear why, says Rafael Harpaz, a medical epidemiologist in the Centers for Disease Control and Prevention's division of viral diseases. More than half of cases occur in people over age 60, when the risk of complications also rises steeply. Women are slightly more likely to contract shingles than men.
The CDC has urged all Americans age 60 and older to get the shingles vaccine—whether they've had shingles or not. But supplies of the vaccine are on back order in some areas. Merck & Co., the only company that makes it, has encountered frequent supply problems since the vaccine was approved in 2006.
Shingles is caused by the Varicella zoster virus, or VZV, the same virus that causes chicken pox, and it only strikes people who have had chicken pox in the past. Like other herpes viruses, VZV never fully leaves peoples' bodies. It can lie dormant for decades in the nerve roots in the spinal column, until it suddenly replicates and travels down the nerves to cause shingles. This frequently creates a striped rash that follows the pattern of nerves on the back or chest.
Exactly what prompts the virus to wake up is unknown, but it seems to occur when the immune system, which has kept it in check for years, becomes weakened due to age, illness or treatments such as chemotherapy. Emotional stress can cause recurrences of other herpes viruses, and the CDC is investigating whether it can spark shingles as well.
For the new study on shingles recurrence, researchers at the Olmsted Medical Center in Rochester, Minn., examined medical records of nearly 1,700 patients who had a documented case of shingles between 1996 and 2001. They found that more than 5% of them were treated for a second episode within an average of eight years—about the same rate as would typically experience a first case.
That a recurrence is so common is more of a surprise to virologists and other scientists than primary-care physicians, who have seen it in their practices, says Barbara Yawn, director of research at the Olmsted center and the study's lead author. "I've gotten calls and emails from some saying, 'Thank you. Now they will believe us.'"
The Olmsted researchers found the people most likely to have a recurrence were patients whose pain had lasted more than 30 days with their first shingles episode.
It's possible that some subgroups of the virus are more prone to recurrence, says Dr. Yawn. In their next study, her team is monitoring new episodes of shingles and the CDC will analyze samples of those that recur to look for genetic patterns. The earlier studies were funded in part by Merck and the National Institutes of Health, while the new study is funded by the CDC.
Some shingles cases are mild, causing only a minor rash. But some patients develop sharp, stabbing nerve pain that can make the affected area extremely sensitive. "Sometimes people say they can't stand to have anything touch the rash area, even clothes," Dr. Yawn says.
In some cases, the nerve pain is the only symptom for days. Patients have been hospitalized with what was thought to be heart disease or appendicitis until the telltale shingles rash appeared. "Sometimes the rash never develops—that really confuses doctors," says the CDC's Dr. Harpaz.
Nerve pain that lingers for more than a month is called postherpetic neuralgia, or PHN, and it can last for years in some patients. While antiviral medications can shorten the duration and severity of shingles episodes, PHN is harder to treat. Some patients get limited relief from opiates, antiseizure medications and antidepressants, but many elderly people can't tolerate the side effects.
In rare cases, shingles has other serious consequences. Blisters can become infected. A rash on the face can spread shingles into eyes, which can lead to loss of vision, sometimes permanent. A rash around the ear can cause a complication known as Ramsey Hunt syndrome, which can include deafness and weakness of the facial muscles.
A big unknown is whether people who got the chicken-pox vaccine as children will be susceptible to shingles in later years or protected from it—or even vulnerable to full-blown chicken pox if their immunity has weakened. Since the chicken-pox vaccine was only approved in 1996, it will be several decades before the first generation of Americans to be widely vaccinated reaches the typical shingles years.
"It's quite plausible that rates will come down dramatically as those kids become older adults," says Dr. Harpaz, though he notes that some people who got the chicken-pox vaccine may unknowingly harbor the actual virus because the vaccine doesn't prevent 100% of cases, and some people may have had a mild, unnoticeable case before they were vaccinated.
The shingles vaccine, known as Zostavax, doesn't eliminate all cases. Studies show that it cuts the risk of shingles by about half in people over age 60. The cases that do occur in vaccinated people tend to be milder.
If it's possible to get shingles more than once, why does a vaccine work at all? Eddy Bresnitz, Merck's medical director for adult vaccines, says that unlike most vaccines, which prime a person's immune system to ward off a virus the first time it invades, Zostavax boosts the immune system's ability to keep the preexisting herpes infection in check, even though it never fully disappears.
To date, less than 11% of Americans over age 60 have had the shingles vaccine, partly because the shortages have frustrated public-awareness efforts and partly because of cost. Zostavax, which ranges from $140 to $400, is one of the most expensive of adult vaccines, and only some Medicare Part D plans cover it.
Dr. Bresnitz says Merck is building a new plant in North Carolina and expects to have more Zostavax available in coming years. It uses the same raw materials as the chicken-pox vaccine for children, to which Merck gives first priority. People can check for local availability of the vaccine at www.Zostavax.com. Side effects are usually limited to mild irritation and tenderness around the injection site.
Public-health experts urge Americans over 60 not to wait until they are very old or ailing to get the vaccine. Once people have compromised immune systems, they are no longer eligible, due to the risk that the vaccine could cause shingles rather than prevent it.