I Got a Fever After the Flu Shot—Here’s Why That’s Totally Normal
I have an amazing knack for catching every sickness that goes around. Cold season? I’m sick. Stomach bug circulating? Yeah, I’ll get it.
So, when it’s flu season, you better believe I’m getting my flu shot. I know that getting the vaccine doesn’t mean I’m completely protected against the flu (I mean, who am I kidding with my luck?) but as a health reporter, I’ve done enough stories on otherwise healthy people who have died from the flu to make me want to get any protection I can—even if it just means I’ll get a more minor case of the illness.
With that in mind, I got my flu shot on Wednesday. And by Wednesday night, I came down with a fever. I had chills, sweating, and all the other fun stuff that comes with a fever. So, I bundled up in bed, took some acetaminophen, and tried to sleep it off. The next morning, it was back. I took some acetaminophen again, and went about my day. And, by that evening, I had a low-grade fever again. WTH?
Wait, can the flu shot really cause a fever?
Turns out, you can get a fever after the flu shot. And, while it’s not super common, I got it. Because of course I did.
It’s important to make this clear up front: You can’t get the actual flu from the flu vaccine. “What’s in the vaccine is only part of the flu virus,” explains William Schaffner, MD, an infectious disease specialist and professor at the Vanderbilt University School of Medicine. “It can’t in any way reconstitute and make you sick.”
When you get the flu vaccine, it stimulates your immune system to develop antibodies to protect you against the flu, explains infectious disease expert Amesh A. Adalja, MD, senior scholar at the Johns Hopkins Center for Health Security. “Your immune system is turning on and reacting to the vaccine, and that can cause a fever,” he says.
It can also cause other side effects associated with the flu shot, muscle aches, headaches, fatigue, and pain or swelling at the injection site.
How long does this fever usually last?
It shouldn’t be more than a day or two, Dr. Adalja says. “It’s not usually something that interferes with your life,” he adds.
What can you do if you get a fever after the flu shot?
If it’s bothering you, you can take acetaminophen, Dr. Schaffner says—that should bring the fever down. But, if it’s a minor fever and you otherwise feel okay, he says you’re fine to just let it ride.
It’s important to point out that your fever with a flu shot should be pretty minor, like a degree or two above your usual. (Mine was 100.5 at its worst.) “If it’s really high, prolonged, or you feel badly, call your healthcare provider,” Dr. Schaffner says. “Something else might be going on at the same time.” Translation: If your fever is high and not going away, it’s possible you already caught the flu—or another circulating virus—before the vaccine had time to go into full effect (which often takes about two weeks).
Sure enough, I feel pretty okay today so, fingers crossed, I’m healthy again.
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