Did My Flu Shot Give Me the Flu?

I just got my flu shot two days ago, so why do I feel like this? 

 To wake up with a runny nose is usually just a nuisance, so I carry some tissues in my pocket and go about my day. A couple hours laters and I feel this gradual headache setting in. An unusual sense of  fatigue and some achy muscles by mid-afternoon tell me I should probably go to bed early tonight. A few hours later with two sprays of Afrin in each nostril and 650 mg of Tylenol,  I tuck myself and it’s lights out for me. Rather than wake up feeling rejuvenated and well-rested, I wake up feeling the same, plus now I am shivering and have a fever! Sounds like I have the flu. But wait…. I just got my flu shot two days ago. Did the flu vaccine give me the flu? 

I’ll just throw out the answer right now…. No. Let’s take a closer look at why the influenza vaccine is not the culprit here. Influenza, or what we call ’the flu’, is a viral infection that targets the nose, throat and lungs. When it comes to viruses, there are a few different ways a vaccination can be made to effectively work in providing protection for someone. The influenza vaccine has a few types in the US: live attenuated, inactivated, and the recombinant vaccine. 

The live attenuated vaccine weakened forms of the virus. This is administered into our body so that the immune system will recognize the virus and launch an immune response. The immune response involves destroying the invading virus and generating memory cells so that our body will develop immunity against it. It’s important to point out that the virus in this form is too weak for it to cause infection in our bodies. It is also too weak in this form to grow in our lungs, so it is a very safe and effective method and will not cause someone to become sick with the flu. 

The inactivated influenza vaccine contains dead particles of the virus. Most people do not have issues with this vaccine once they hear that the virus is actually dead in this vaccine. What happens is that these dead particles that are administered into the human body will be recognized by the immune system, antibodies will be generated, and the memory cells will work hard for us to have immunity against that particular virus. This type of vaccine is completely incapable of causing the flu. 

The final type we use in the US is the recombinant influenza vaccination. This type is a little different in that a protein from the influenza virus is isolated and incorporated into a vaccine. For the influenza virus, a surface protein called hemagglutinin is used. When this type of vaccine is administered into our bodies, our bodies build up the machinery it needs to fight the hemagglutinin molecules and build immunity. When our bodies comes into contact with influenza later, our immune system will recognize it, destroy the hemagglutinin proteins and, thus, the virus will be destroyed as well. Because this vaccine only contains a small piece of the influenza virus, it will surely not cause one to fall ill with the flu.

So there you have it. The various influenza vaccines will not cause you become sick with the flu. The point of a vaccine is to trigger an immune response, so you should always anticipate some symptoms for a couple days. If you really did become sick with the flu after receiving your vaccine, keep in mind that you may have contracted the flu before your vaccine was effective, or even contracted the flu before you received your vaccine. It’s always important to acknowledge that the flu vaccines changes annually to anticipate the most viral strain for that year. It is not impossible for year to become ill with a different strain of influenza than the one you were immunized for. If you’re hesitant about getting your influenza vaccine, think about the people sick with severe disease who are so immunocompromised that they cannot even receive a vaccine. Your vaccine may be their only protection against disease.