Infections and Flu Shots

Content provided by the Faculty of the Harvard Medical School

Anthony Komaroff, M.D., is professor of medicine and editor-in-chief of Harvard Health Publications at Harvard Medical School. Dr. Komaroff also is senior physician and was formerly director of the Division of General Medicine at Brigham and Women's Hospital. Dr. Komaroff has served on various advisory committees to the federal government, and is an elected Fellow of the American Association for the Advancement of Science.

Question:

Are there times when an otherwise healthy person should not get a flu shot? I have shingles. Is it okay for me to get a flu shot now?

Answer:

You ask a good question. Unfortunately, the question has not been studied extensively. In general, doctors recommend that people not have a vaccine when they are fighting an infection.

Why is this? The purpose of a vaccine is to introduce into your body an infectious agent (or pieces of that agent). Your immune system then recognizes the invader and builds up resistance to it. This would protect you in the future if you got the real infection. Your immune system would be ready to attack it.

But if you already have an infection, your immune system is focusing on that infection. If you get a vaccine now, your immune system might not pay attention to it, and so you would not be as protected in the future.

This is a theoretical argument. It has not been solidly proved through scientific studies.

Your shingles is an active infection. For that reason, if you were my patient, I would recommend that you wait to get the flu shot until the shingles greatly improves or goes away completely. You should check with your doctor about this, however.

Even if you have to delay getting the flu shot, don't go without it. At your age (72), you are at higher risk from getting the flu, and the flu shot offers powerful protection.

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If you have the flu, you are contagious one day before symptoms appear and up to five days after.