The Flu Vaccine Myth

hand holding syringe isolated on white

Flu season is well upon us, and the final end-of-semester “push” is over for most of us.  Have you ever noticed how you always seem to get sick immediately after Finals are over?

Yeah, there’s actually a good reason for why that happens.  It has to do with your stress hormones, but that’s a whole other blog post.  Today I want to talk about something entirely different.

Has anybody ever told you that the last time they got a flu shot, it gave them the flu? Or that they didn’t want to get the flu vaccine because they were afraid that they’d come down with the flu?

Is that true? CAN you catch the flu from the flu vaccine?

Usually, the answer is no, but there are a few caveats.  First, it depends on the type of flu vaccine you get.  There are two:  the traditional injection, and the relatively newer nasal spray.

You absolutely do not get the flu from the traditional injection.  These vaccines inoculate using either deactivated flu virus, or “pieces” of flu virus (recombinant type).  The goal is to “show” your immune system just enough of what that flu strain “looks like” so that your body can create antibodies to be ready in case the real flu virus enters your body later in the flu season.  Whichever version you receive, the flu virus will be non-functioning, so it cannot multiply and spread throughout your body.

The nasal spray, on the other hand, contains live, attenuated virus.  “Attenuated” means weakened, and according to the Centers for Disease Control and Prevention (CDC) website this strain of flu virus is weakened to the point that it is impossible for the virus to actually infect your body.  In addition, the CDC explains that the virus found in the nasal spray has been “cold-adapted,” meaning that these viruses are only activated at lower temperatures.  In the case of our bodies, these lower temperatures are found in the nose where the vaccine is administered.  If any of the vaccine virus were to find its way into the warmer parts of the body such as the lungs, the virus would be unable to replicate.

So the official answer is:  no, the flu vaccine cannot cause the flu.  But I have to admit that my gut (and my common sense) tells me that, under certain conditions, it might be possible to catch the flu from the live but attenuated nasal spray version…just don’t admit that on a test 😉

So why do so many people think they catch the flu from the flu vaccine?

There’s at least three reasons why people mistakenly believe that they’ve caught the flu after getting the vaccine.  The first is that they misunderstand the symptoms that they are having.  Just because you have a runny nose, body aches, and even a fever does NOT mean that you have the flu…it means that your immune system is doing its job.

Remember back in A&P (and Pathophysiology, and Microbiology…)?  The immune system cells in a healthy person are always busy looking for invaders.  When they find an invader, such as the virus “look-a-likes” found in a flu vaccine, the immune system starts attacking.  Attacking involves creating antibodies, yes; but also histamine reactions that cause inflammation, excess fluid, and possibly cell lysis.  Plus, this immune response might trigger a mild body temperature increase that helps the white blood cells to work more effectively.  So as you can see, what many people interpret as symptoms of the “flu” are actually the symptoms of their immune system responding appropriately to the vaccine.

A second reason that people might think they caught the flu from the flu vaccine is because it can take up to two weeks before the flu vaccine has prompted the body to create enough antibodies to be effective.  So if you were already exposed to flu before getting vaccinated, or if you become infected within that 2-week window of time, then it might seem like you “caught” the flu from the vaccine.  But in reality, it was just a coincidence.

A third reason why people sometimes believe they caught the flu from the vaccine is because the vaccine is not 100% effective at preventing the flu!  In fact, I don’t know of any vaccine that is 100% effective at preventing anything.  But some research suggests that if a vaccinated person contracts the illness that they were vaccinated for, then the length and/or severity of that illness may be decreased.  However, many people still incorrectly believe that it’s impossible for them to contract an illness they’ve been vaccinated for.

Should you get the flu vaccine?

Probably…at least if you want to continue your nursing education or stay employed at a healthcare facility.  The flu vaccine is often an annual requirement in those cases, but of course you should check your school’s policy to make sure.

That being said, there’s several good reasons why someone may choose not to get the flu vaccine if it’s not required for them.  Many people don’t think that the evidence supporting the flu vaccine is as strong as the medical establishment (and the media) make it out to be.  Dan Clinton at wrote a great analysis of flu and vaccine statistics earlier this year that I would encourage you to read.  As scary as TV makes the flu sound every year, when you examine the actual number of confirmed flu cases and their consequences, it really isn’t as bad as most people think.

There are some other good reasons not to get the vaccine, too, and some of them you might someday see on an exam.  For example, the flu vaccine is not approved to be given to babies less than 6-months old.  And if you currently have a moderate to severe illness, then you should wait until you’re feeling better before getting the vaccine.  Also, having a history of egg allergy or Guillain-Barre Syndrome is a red flag that needs to be discussed with a doctor before getting the vaccine, because the flu vaccine can trigger serious complications for people with those conditions.

Are you planning to get the Flu Vaccine this year?  Why or why not?

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