Unlikely Allies: The Flu Shot and Your Immune System

by Leigh Ann Otte

Seems like your immune system and the flu shot would be mortal enemies—fighting to the death. But that would mean they’d both have to be alive to start with. And they’re not. The flu shot’s dead, poor thing.

Besides, it and your immune system are on the same side, working together to help you battle the flu shot’s evil twin: the live flu.

Internist Bruce Heckman explains in this week’s featured article, “Flu Shot With a Compromised Immune System: Good Idea for Most”:

When a healthy person gets sick, the body produces antibodies in the blood to help fight off the disease. The flu shot works because of this mechanism. It contains dead flu viruses that trigger the body to produce specific antibodies to combat the flu strain (or strains) going around that year. Because the shot only contains dead viruses, it doesn’t actually give you the flu.

Though we hear about people getting flu-like symptoms after the shot every year, the CDC says it’s rare for that to happen. When it does, the yuckiness doesn’t last more than a couple of days.

Do you usually get the flu shot? Why or why not?



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2 Responses to “Unlikely Allies: The Flu Shot and Your Immune System”

  1. Judy Rodman Says:

    Great clarification here, but question: What does cause the inflammatory-like symptoms that some experience after getting the flu shot?
    Judy Rodman recently posted..How Crying Affect the Voice

  2. lotte Says:

    Good question, Judy.

    The CDC doesn’t explain that on their site, so I asked the creator of this site, James Hubbard, M.D., what causes some people to feel sick after getting the flu shot. He says, “My own opinion is the inflammation, body aches and flu-like symptoms are a side effect of your body’s immune response fighting off the antigen (dead flu virus). To me, it’s like some people who feel horrible with pollen allergies. Also similar to your body’s response when you’re truly sick.”

    He points to a good explanation of inflammation at the NIH website MedlinePlus. It says: “The inflammatory response (inflammation) occurs when tissues are injured by bacteria, trauma, toxins, heat, or any other cause. The damaged cells release chemicals including histamine, bradykinin, and prostaglandins. These chemicals cause blood vessels to leak fluid into the tissues, causing swelling. This helps isolate the foreign substance from further contact with body tissues.”

    The CDC says any (unlikely) sick feeling after a flu shot is usually gone by a couple of days. Supporting that idea, Dr. Hubbard notes, “Histamines, bradykinins, prostaglandins kick in big time for a day or two.”

    The MedlinePlus inflammation page is here: http://www.nlm.nih.gov/medlineplus/ency/article/000821.htm

    The CDC flu shot page is here: http://www.cdc.gov/flu/about/qa/flushot.htm

    The CDC does note that, rarely, serious reactions occur. You can read about the symptoms at their site.

    Leigh Ann Otte
    Managing Editor

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