October 28, 2008
by Harvard Health Letters
Vaccinations aren't just kid stuff anymore, and now there's another one that older Americans are being urged to get in addition to their annual flu shot, the pneumococcal pneumonia vaccine at age 65, and a tetanus booster every 10 years. The Advisory Committee on Immunization Practices, which sets vaccine policy for Americans, made its official recommendation for the shingles vaccine in 2008. All Americans ages 60 or older should get the shot, the committee says, even if they've already had shingles.
The committee's recommendation of the need for the vaccine after shingles is a departure from the U.S Food and Drug Administration-approved instructions for the vaccine (the package insert), which is silent on the subject. And it contradicts a question-and-answer sheet posted on the agency's Web site when the vaccine was approved, which suggests that it's unnecessary after you've had shingles because "it's unlikely that people who have had shingles will suffer from them again."
It's difficult to gauge the practical effects of the recommendations. Doctors may be more inclined to urge their patients to get the vaccine. But insurance coverage is spotty. For example, Medicare Part B, which covers flu shots and pneumococcal vaccine, doesn't cover the shingles vaccine. Pricing varies, but the total bill, including the doctor's fee, can come to several hundred dollars. And the vaccine is no guarantee: results from the Shingles Prevention Study, the 39,000-person trial that laid the groundwork for FDA approval, showed that about half the time the vaccine did not protect people against shingles, although it did do a better job in preventing postherpetic neuralgia, prolonged pain that develops and continues after the typical rash disappears in about 10 percent to 15 percent of people with shingles.
Another reason people have doubts about the vaccine is fear that it could give them shingles. The vaccine is made with a weakened virus, and there are rare instances of "live attenuated" vaccines causing the very disease that they're supposed to prevent. It doesn't happen often, but the live attenuated version of the polio vaccine can cause polio, for example. But from the data reported so far, and from what is known about the disease, fears of contracting shingles from the shingles vaccine are misplaced.
Like any medical intervention, shingles vaccine is a balancing act. The cost and any lingering questions about safety need to be weighed against the benefit: a 50-50 chance that it will keep you from getting shingles and 66 percent chance that it will prevent postherpetic neuralgia. It's not pleasant, but most people get through shingles just fine. Postherpetic neuralgia is another story: it can last for months, even years, and be quite debilitating. Cutting the risk of that happening by two-thirds would tip the balance for some people, but maybe not others.
DORMANT NO MORE
The medical term for shingles is herpes zoster, which is often shortened to just zoster. It's caused by the varicella-zoster virus, the same virus that causes chickenpox. After a case of chickenpox is over, the varicella-zoster virus can lie dormant in the nerves that carry sensory signals (touch, pain, and so on) to the spinal cord and brain.
Shingles occurs when the virus re-emerges, like Greeks from the Trojan horse, and becomes active again. Nerves, skin, and other nearby tissues get inflamed. More serious damage to nerve tissue leads to the long-lasting pain of postherpetic (after herpes) neuralgia (the term for pain along the course of a nerve.)
A healthy immune system (particularly the T cells) seems to keep the varicella-zoster virus in check, so conditions and treatments that weaken the system are associated with shingles. For example, people with Hodgkin's disease, a cancer that affects the infection-fighting lymph system, are vulnerable to getting shingles, as are those infected with the human immunodeficiency virus (HIV). A few studies suggest that shingles occurs more often during the summer, so some have proposed a possible link to ultraviolet light.
But the clearest connection is to advanced age, which makes sense because the immune system, like other parts of the body, loses vim and vigor in the later decades. By some calculations, half of us who make it to age 85 will have experienced shingles along the way. The risk of postherpetic neuralgia also increases with age.
In 2007, Mayo Clinic researchers reported the results of a study that included 1,669 adult residents of Olmsted County, Minnesota, who had confirmed cases of shingles. (The Mayo clinic is located in Olmsted County.) They found that about 20 percent (50 of 246) of the people who got shingles when they were 80 or older had pain that lasted three months or longer, compared with just 5 percent (17 of 314) of those ages 50 to 59.
The classic shingles symptom is a painful rash on the trunk that's limited to one or two dermatomes, areas of the skin supplied by a single nerve. People describe the pain -- which often comes before the rash -- as burning, throbbing, or stabbing. The rash usually lasts a week to 10 days and heals completely in two to four weeks. If postherpetic neuralgia develops, the pain can be severe, and conventional painkillers usually don't help much.
Classic shingles is just one of the problems that reawakened varicella-zoster can cause. Sometimes there's pain and skin sensitivity but no rash. Arms and legs may feel weak if the nerves that control their movement are affected. If the virus is in the ophthalmic branch of the trigeminal cranial nerve, parts of the eyes and the eyelids get inflamed. Some researchers believe that up to a quarter of cases of Bell's palsy, a condition that causes facial paralysis, may be caused by varicella-zoster virus.
The varicella-zoster virus can be beaten back with antiviral medicines, reducing the pain associated with shingles and possibly the chance of postherpetic neuralgia developing. Some studies show that taking an anti-inflammatory like prednisone along with an antiviral helps reduce the pain from shingles and makes the rash heal faster.
Acyclovir (Zovirax) has been the mainstay among the antivirals, but it needs to be taken five times a day. Valacyclovir (Valtrex) only needs to be taken three times a day, and in a head-to-head trial, it proved to be more effective than acyclovir. But valacyclovir is also more expensive, so your insurance may not cover it. Famciclovir (Famvir) is another antiviral.
Regardless of which one is prescribed, the antiviral medications are most effective if they're taken as soon as possible after shingles has started. In clinical trials, treatment has tended to begin within three days of the rash appearing. It's unclear how effective the medicines are when started after that, although there's nothing about the biology of shingles that would suggest that three days is an absolute cutoff. As a practical matter, many physicians treat shingles as soon as possible after the diagnosis and then hope for the best.
The shingles vaccine, a Merck product sold under the brand name Zostavax, is made with the same strain of the varicella-zoster virus (the Oka/Merck strain) as the chickenpox vaccine that children get, but it's at least 14 times stronger.
Some research suggests that the immunity from the vaccine wanes, so eventually there may be recommendations for booster shots. For now, though, the vaccine consists of a single shot in the upper arm.
People have the usual reaction to a vaccination: redness, soreness, and some swelling at the injection site. Occasionally there's a headache afterward. In a subset of the Shingles Prevention Study designed to study adverse reactions, more people in the vaccine group had a serious medical problem after receiving the shot than those who were in the placebo group (1.9 percent vs. 1.3 percent). But in the judgment of the Advisory Committee on Immunization Practices, neither the timing nor "clinical patterns" suggested a causal connection to the vaccine.
CAN IT GIVE YOU SHINGLES?
A tiny percentage of people get either a zoster-like or chickenpox-like rash within a month or so of getting the vaccine. In the prevention study, it was just 0.3 percent (55 of 19,270 subjects).
When we contacted Merck, we were told the company knew of 241 cases of shingles that had been reported by health care providers among the over 1.3 million Americans who had gotten the vaccine during its first 15 months on the market. That works out to an even smaller percentage -- 0.02 percent.
Is this evidence that the shingles vaccine gives some people -- however few they may be -- shingles or chickenpox? Not necessarily. Remember, the vaccine is only partly effective, so some of these cases are breakthrough infections caused by "natural" varicella-zoster virus that the person was harboring or was recently infected with -- not the weakened Oka/Merck strain that people have been injected with. In fact, by some estimates, you would expect about 5,000 cases of "natural" shingles for every million persons getting the vaccine.
Researchers, using a technique called polymerase chain reaction (PCR), can test a shingles or chickenpox rash for genetic evidence of Oka/Merck or a natural strain of the virus. In a small, Merck-sponsored study, the vaccine strain was detected in two people's rashes. But otherwise all of the PCR test results reported so far have pointed to the natural strain as the cause of the post-vaccination rashes. The catch is that only a handful of PCR tests have been done. It's possible that some of the rashes caused by the vaccine were among those that hadn't been tested.
NEEDED AFTER HAVING HAD A CASE?
People who have experienced shingles might be among the most eager to get the vaccine if it markedly improved their chances of not getting shingles again, so it's significant that the immunization committee recommended the shot even for people who've had shingles.
The committee made its recommendation for two basic reasons. First, blanket recommendation eliminates the need for sorting through medical histories that may not be all that reliable. The diagnosis of shingles isn't such a sure thing: doctors mistake shingles for other conditions, and the other way around. And there's no blood test to check for antibody evidence of a past case.
Second, researchers are finding that some people get shingles again after getting over their first case. The thinking had been that recurrence is only a problem for people with compromised immune systems. In the Mayo Clinic study, 24 of the 1,669 shingles sufferers had a second episode. That's a small percentage (1.4 percent), but given that perhaps as many as a million Americans come down with shingles every year, the vaccine, at 50 percent effectiveness, could prevent over 5,000 recurrent cases each year.
Whether it actually will is a different question, which can be answered only with time and further research. - Harvard Health Letter
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