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Feeling Flu-y After A Flu Shot? Doctors Explain Common Side Effects

TL;DR? Flu shots cannot give you the flu.

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Recently, there's been as much conversation happening about the possible side effects of the flu vaccine as there has been discussion surrounding the flu itself. There are a lot of misconceptions out there about the flu shot, and what it means for you as a patient and as a parent. If you've recently decided to go ahead with the yearly vaccine, you might wonder, given all the rumors, if you experience flu-like symptoms from the flu shot, are you contagious? Is it even possible to be contagious after a flu hot? Is flu vaccine inactivated or live virus? To help us debunk flu shot myths once and for all, and to help everyone feel a little more confident getting themselves and their families vaccinated against the flu, we spoke to Dr. Shalika Katugaha, System Medical Director of Infectious Diseases at Baptist Health of Northeast Florida.

Can you get the flu from the flu shot this year or, ever, from any flu vaccines?

“The flu shot is made from an inactivated virus,” explains Katugaha. “This inactivated virus cannot transmit infection. You cannot catch the flu from the flu vaccine. You are NOT contagious after a flu shot.” The flu shot does not give you the flu — it cannot, because the virus is not active. Therefore, you cannot be contagious, because you’re not infected with a virus.

What are the side effects of the flu shot?

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Side effects of the flu vaccine tend to be mild, Katugaha explains, and — thankfully — short lived. Any flu shot side effects that you do experience should only last for 24-48 hours, she says. If you experience flu-like symptoms as a side effect of the flu shot, they should resolve quickly and be far less severe than the actual flu itself, according to the Centers for Disease Control and Prevention (CDC). Common side effects include:

  • malaise
  • headache
  • muscle aches
  • soreness at the injection site
  • nausea
  • fever

“These side effects are a sign that your immune system is responding to the vaccine and getting ready to fight the real flu when you are exposed,” Katugaha reminds. In other words, think of any side effects as a good sign.

Can I still get the flu, even if I’ve had a flu shot?

The vaccine takes approximately two weeks to provide protection from the flu, and “flu vaccination reduces the risk of flu illness by between 40% and 60%” the CDC explains. In other words, it is very powerful, but not 100% protective. So yes, it is still possible to get the flu, even if you’ve had your flu shot. However, you’re much better off catching the flu after having had your flu shot. Even if you catch the flu, the flu vaccine should help your body fight off the infection, and reduce the likelihood that you’ll end up in the hospital.

While it’s true that the side effects of the flu shot somewhat mirror the symptoms of the flu, both the severity and duration of these symptoms are far different. While you might get a low grade fever and experience some nausea and a headache from the flu jab itself, an actual flu infection knocks you for a loop, hard and fast. I was the unfortunate recipient of the flu virus this year, and believe me when I tell you, you know when you have the flu. I had chills so badly my body felt like it would never get warm again, and my head felt like a team of rabid ferrets were fighting on the inside of my skull. My fever was nearly 102 degrees Fahrenheit, my muscles hurt, my skin hurt, and even my hair hurt. It was extreme.

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I get the flu shot every year as soon as it’s released. When I do, I get a relatively unfortunate headache, my arm is usually sore for a day, and I get a bit dizzy when I get jabbed. But, I would experience that 100 times over before ever volunteering to get the flu again. However, if you get the shot, and you notice swelling of your mouth, tongue, or throat, trouble breathing, if you're feeling particularly weak or devoid of color — these are signs of a severe reaction, and you need to be treated immediately, according to the CDC. Severe reactions are extremely rare.

So, if you get flu-like symptoms from the flu shot, are you contagious?

It’s worth saying one more time: “Vaccine reactions are NOT contagious,” Katugaha reiterates. While vaccine side effects (if you experience them) aren’t fun, the real flu is so much worse. This is why the CDC recommends everyone still get the shot if you haven't done so already, because flu season is long, deadly, and may not have peaked yet. Maybe you'll even get a cool Disney Bandaid. I know I did.


Dr. Shalika Katugaha, System Medical Director of Infectious Diseases at Baptist Health of Northeast Florida.

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