Flu Shot Side Effects

Anyone who has experienced the flu (influenza virus), understands how awful it can be. While most people can recover from the flu within 1 to 2-weeks, some individuals can develop life-threatening complications like pneumonia. Thankfully, the flu vaccine can help reduce your chances of getting the virus by as much as 60-percent, according to the Centers for Disease Control and Prevention (CDC).

Just like any other vaccine, the flu vaccine can have side effects. Most side effects are the result of your immune system responding to the vaccine. Some people may experience no side effects, while others may experience mild side effects.  In rare cases, the side effects can be severe. Nonetheless, it’s always good to be aware of what you can expect. Here are a few common flu shot side effects…


One side effect you may experience is a headache. If this does happen, it typically occurs on the first day after receiving the flu shot. The good news is the headache should go away within a couple of days.

Along with headaches, you may also experience mild muscle aches and pains throughout your body. Just like headaches, this usually occurs on the first day and goes away in a couple of days.


After having the flu shot, you may experience a fever of 101-degrees Fahrenheit or less. If you do get a fever it should clear up in a day or two. However, if the fever is bothersome, you might want to take acetaminophen or ibuprofen.

Although it’s worth noting, there are some concerns that medications like acetaminophen or ibuprofen may interfere with the vaccine. Healthline explains, “The concern is that these medications could diminish the body’s response to vaccines.” That said, the research behind these claims is currently not conclusive. If a fever is bothering you, speak with your doctor and they can advise what is best for you.

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A Reaction at the Flu Shot Injection Site

One of the most common side effects of the flu shot is experiencing a reaction at the injection site. The injection is usually given on the upper arm and may produce slight swelling.

You may also experience soreness, warmth, or redness. Thankfully, these side effects typically only last for a day or two.


Another mild side effect you may experience from the flu shot is dizziness or fainting. If this does happen it shouldn’t last for longer than two days.

If you know that you get dizzy or tend to faint following a shot, make sure you notify the medical professional who is administering your shot. Healthline also explains to help prevent this side effect from happening, you can try eating a snack before having the flu shot, and you may also need to sit for a while after receiving the flu shot.

Severe Side Effects From the Flu Shot

While the mild side effects we discussed above are the most common, there are a few severe (but rare) side effects you may want to know too. The first being a fever higher than 101-degrees Fahrenheit. While this is a rare side effect, it could happen.

If you’re worried about your fever, be sure to call your doctor. Next, let’s take a look at a few more severe side effects from the flu shot.

Guillain-Barré Syndrome (GBS)

Some individuals who receive the flu shot may experience Guillain-Barré syndrome (GBS). However, this is extremely rare. Healthline explains, “GBS is a neurologic condition that causes weakness and paralysis throughout your body. However, it’s not clear if the flu vaccine is the actual cause of GBS in these cases.”

If you have experienced GBS in the past, you may be more susceptible to it in the future. Just make sure you inform your doctor if you have a history of this condition to find out if the flu shot is safe for you.

It’s also worth noting, you should call your doctor immediately if you begin experiencing symptoms of GBS after receiving your vaccine.

Severe Allergic Reaction

A severe allergic reaction can happen after receiving the flu shot. However, it is very rare. If you do experience a reaction it will usually develop within a few minutes up to a couple of hours after receiving the flu shot.

Some common symptoms of a severe allergic reaction include dizziness, fast heart rate, difficulty breathing, swelling, hives, and weakness. If you experience any of these symptoms call your doctor. However, if the symptoms are severe call your emergency hotline right away or head to the closest emergency room if you’re able.

Who Should Get the Flu Shot?

Once again, the flu shot doesn’t usually have severe side effects and most people either experience mild side effects or no side effects at all. So the next question is, who should get the flu shot?

The CDC recommends that every individual over the age of 6-months should receive an annual flu shot (with a few exceptions). Individuals who are potentially at risk of serious complications from the flu virus should also get the shot. This includes older adults age 65 and older, anyone with a chronic health condition including their caregivers, and pregnant women.

Who Shouldn’t Get the Flu Shot?

While the flu vaccine is recommended for most people, there are some individuals who shouldn’t get the flu shot. This includes anyone who has had an allergic reaction to the flu vaccine in the past or anyone with a severe allergy to eggs or any other ingredients in the vaccine.

You should also not get the flu shot if you’re currently sick and have a mild or severe fever or have had Guillain-Barré syndrome. When in doubt, consult your doctor to find out if the flu vaccine is suitable for you.

When to See a Doctor

Overall, the flu shot has very few side effects and is considered safe for many individuals. The CDC explains, “Seasonal flu shots protect against the three or four influenza viruses that research suggests may be most common during the upcoming season.” That said, if you are still worried, talk with your doctor. They can help determine whether the flu shot is safe for you as well as explain all the potential complications.

If you do decide to get the vaccine, just be on the lookout for any unusual symptoms following the injection. If you notice any adverse reactions speak with your doctor or if they’re severe seek emergency help right away.

Patty Weasler, RN

Patty Weasler, RN

Patty is a freelance health writer and nurse (BSN, CCRN). She has worked as a critical care nurse for over 10 years and loves educating people about their health. When she's not working, Patty enjoys any outdoor activity that she can do with her husband and three kids.