It is now time for an important exhortation about influenza vaccinations. Here it is: Get a flu shot, especially if you are 65 or older.Influenza is a viral infection that has been responsible for thousands of deaths in the last several years, a majority of which were people 65 or older.

The vaccination works by preparing the body's immune defense system to fight against influenza infection. The best example of an effective vaccination program is the smallpox program. Nobody dies of smallpox anymore because it has been eliminated through an aggressive surveillance and vaccination program.

We probably can't eliminate influenza, but we can cut down greatly on its effects.

One problem, however, is that the virus is constantly mutating. If our immune system has learned to fight off one year's strain, the virus can change its "appearance" slightly, come back next year and fool our defenses.

That is why it's necessary to get a flu shot every fall. Scientists around the world are constantly tracking the virus and figuring out what "costume" the virus is going to wear this year in the Northern Hemisphere. A vaccine then is produced to teach our defenses to recognize this year's strain and thwart it.

The vaccine is safe. Its immediate side effects may include a temporary sore arm or, less commonly, a sluggish feeling for one or two days.

The virus contained in the vaccine is inactivated or killed, so tha it is impossible to get the flu from it. Every year, however, I have a couple of patients who become sick one or two weeks after getting their vaccination. Although they blame the flu shot for their illness, the two really aren't connected. Their illness was probably inevitable.

I recommend that all of my patients over age 65 get a flu shot, with November being the best time. The only exceptions are: patients who are allergic to eggs and patients running a fever. It is OK to get a vaccination if you just have a cold and no fever; for those with a fever, wait until you get well.

The vaccination is not reserved exclusively for those 65 or older. Younger patients with heart and lung disease, and people who come in contact with a variety of people, especially the very young or the very old, should also get flu shots. By getting a flu shot, an individual will also reduce the chance of spreading influenza among his contacts.

Send questions to: On Aging, The Baltimore Sun, 501 N. Calvert St., Baltimore 21278. Personal replies cannot be provided.

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