Q. Is it a good idea to get the Zostavax vaccine if I've already had shingles and still suffer from mild post-herpetic neuralgia [a type of nerve pain that's the most common complication of shingles]? Will the vaccine prevent future occurrences?

This one's a no-brainer if you're 60 or older: Yes, it's a good idea to get the Zostavax vaccine, and the sooner the better.

If you've already had shingles (herpes zoster), there's no guarantee that you won't get it again and again. That's why the vaccine is so important. And if you happen to get shingles again after vaccination, the episode will likely be shorter and much less troublesome.

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Anyone who has ever had chickenpox is at risk of shingles, which is is caused by a reactivation of the dormant chickenpox virus. You can get shingles at any age, but the risk increases dramatically as you get older and your immune system becomes less effective. Each year up to 1 million Americans — more than half of them 60 or older — are diagnosed with shingles.

Fewer than 15 percent of all U.S. adults 60 and older have gotten the shingles vaccine, according to the Centers for Disease Control and Prevention.

Shingles usually starts with a headache and then a rash on a band or section of skin, typically on one side of the face or body. The rash then turns into clusters of blisters, which fill with fluid and crust over. Shingles can be very painful. The virus travels along nerve pathways, causing inflammation and damage. The pain tends to be more severe and last longer in older people. In the worst cases, the shingles virus can cause blindness, if it infects the eyes or the area around your eyes, as well as hearing problems, brain inflammation (encephalitis) or death.

A study published this year in the Journal of Internal Medicine, based on a study of nearly 200,000 patients, found the shingles vaccine to be "generally safe and well tolerated." The vaccine reduces your risk of shingles (by 51 percent, according to one large study) but does not eliminate it, and the vaccine does not treat or lessen lingering nerve pain from a past outbreak.

Side effects include headaches and mild injection-site allergic reactions, but these typically disappear quickly. Some people suffer more serious allergic reactions such as wheezing or difficulty breathing or swallowing.

You shouldn't be given the Zostavax vaccine if you are allergic to neomycin (or any component of the vaccine) or if you have a weakened immune system.

Researchers are still trying to determine how long a dose of Zostavax vaccine provides protection against shingles and the need, if any, for booster shots.

While Medicare Part B does not cover the shingles vaccine, the government requires that all Medicare Part D plans do. (If you have private insurance, your plan might not cover the vaccine.) Most physicians don't stock the vaccine, which must be stored in a freezer, but they can write you an order for the vaccine, which you can then get at one of the more than 12,000 pharmacies nationwide that provide it.

In my experience, your Medicare Part D copay is likely to be in the range of $60 to $80. That may seem like a lot, but take it from me: If you're unlucky enough to get shingles, you'd pay a million dollars to get rid of it.

Ask the Pharmacist is written by Armon B. Neel Jr., PharmD, CGP, in collaboration with journalist Bill Hogan. They are coauthors of Are Your Prescriptions Killing You?, which was published in July by Atria Books.