Can a Flu Vaccine Give Me the Flu?

Dr. Paul Offit explains why it is not possible to get influenza from the influenza vaccine.


Can a flu vaccine give me the flu?

Paul Offit, MD: Hi, my name is Paul Offit, and I'm talking to you today from the Vaccine Education Center at the Children's Hospital of Philadelphia. One common question that people ask is, can you get flu from the flu vaccine? Well, the short answer to that question is, no. I mean, the way that influenza virus works is it, the virus attaches to your nose and throat. It reproduces itself hundreds of times, thousands of times. Then, it travels down to the lungs and can cause severe and fatal pneumonia, causes high fever, headaches, muscle ache, joint ache, and occasionally severe and debilitating and fatal pneumonia, occasionally. So that's influenza.

Now, the influenza vaccine, however, is not that. There's different ways that the influenza vaccine is made. You can take influenza virus and grow it up in eggs and then fully inactivate the virus. Or you can take the virus and grow it up in mammalian cells and fully inactivate the virus, and even, frankly, purify it from that point on, so that you’re really just seeing the two proteins that sit on the surface of the virus, so-called hemagglutinin and neuraminidase. Or you can use recombinant DNA technology that just makes one of those proteins, the hemagglutinin.

Now, there is one vaccine, so-called FluMist®, which is a live weakened form of the virus, an attenuated, highly attenuated form of the virus, and the way that it's attenuated is it has so-called temperature-sensitive mutations. Therefore, it can only reproduce itself in the nose, which is about two degrees cooler than the rest of your body. So, it can't possibly travel down into your lungs and cause pneumonia because the virus cannot reproduce itself at body temperature.
So, the short answer is, you can't get flu from the flu vaccine.

Thank you.

Related Centers and Programs: Vaccine Education Center

Last Reviewed on Jan 10, 2022