Ask Dr. K: Vaccine can reduce severity even after you’ve had shingles

When the virus reactivates, the infected nerves, and the skin the nerves go to, become inflamed. This causes a burning or stabbing pain. Two or three days later, when the virus reaches the skin, a rash of blisters appear along the affected nerve. The skin may be very sensitive, unable to tolerate even the lightest touch.

About 10 percent of adults who get shingles experience long-term pain, even after the rash has healed completely. This condition is called post-herpetic neuralgia. It may last for months, or even years. It can be quite debilitating.

If you have never had chickenpox, do you have to worry about getting shingles? Unfortunately, yes. For one thing, many people get infected with the virus but don’t get chickenpox — or have such a mild case that no one notices that they have it.

Secondly, even if you are an adult and really never have been infected with the virus, you can catch it from contact with a person who has either chickenpox or shingles. That’s because the virus is in the fluid of the blisters that form.

There is a simple blood test to determine if a person has been infected by the virus. However, I don’t recommend getting it routinely. That’s because it can be falsely negative: The test may say you have never been infected with the virus, but better tests show that you have.

Adults age 60 and older should get a vaccine called Zostavax. Some authorities recommend getting the vaccine at age 50 or older. The vaccine is a shot, given just once.

The vaccine is good, but far from perfect. It reduces the risk of developing shingles by about 50 percent. More important, if you get the shingles vaccine and still develop shingles, it reduces the risk of developing post-herpetic neuralgia by about two-thirds.

You asked if a person who already has had shingles needs to get the vaccine. Yes, you should. The U.S. Centers for Disease Control and Prevention (CDC) recommends that adults age 60 and older get the shingles vaccine even if they have already had shingles, because shingles can come back. After the first flare-up or reactivation of the sleeping virus, it goes “back to sleep” inside your nerves — and it can flare up again.

When you have an attack of shingles, your immune system is engaged in waging war against it. I’ve had patients who did not get the shingles vaccine, and then got shingles. I wait until their attack of shingles is gone before giving the vaccine, as there is some evidence that the immune system responds more vigorously to the vaccine when it is “at rest.”

(Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.)