Having a fever of 101°F or less is one of the most common flu vaccine side effects. A slight fever is deemed a mild side effect. And it should go away within a day or two. If the fever bothers you, though, you can take acetaminophen or ibuprofen.
Some concerns about acetaminophen and nonsteroidal anti-inflammatory drugs, including naproxen and ibuprofen, have been raised.
The problem is that these medications could diminish the body’s response to vaccines. However, research isn’t conclusive as of yet. A fever greater than 101°F isn’t expected. But if you’re concerned about a high fever, call your doctor immediately.