Flu Shot: Learn the Side Effects

Flu Shots

Every year, people protect themselves from the flu by getting vaccinated. The vaccine, which comes in the form of a shot or a nasal spray, can reduce your chances of getting the flu by as much as 60 percent.

The shot is usually recommended for everyone 6 months of age or older. Anyone at risk for developing serious complications from the flu should also receive the flu shot, including pregnant women, people over 65, and individuals with chronic diseases and their caregivers. The shot is not recommended for people who have allergies to chicken eggs or people who have had an allergic reaction to the shot in the past. If you are sick and have a fever, the CDC recommends waiting until you are better to get the shot.

Though side effects don’t always happen to everyone, they can range from mild to severe and often depend on the type of vaccine you receive. Before you get your shot, get educated on the possible side effects.

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Pain at the Injection Site

The most common side effects of the shot happen in the place where the shot was given. After the shot is administered, soreness, redness, warmth, and in some cases, a slight swelling can occur. Soreness at the injection site is the most common side effect. This pain and soreness usually lasts less than two days.

Aches and Pains

Sometimes you might experience some achiness and pain in the muscles throughout your body after the shot. Like the pain at the injection site, this usually happens on the first day and goes away within one to two days. Taking pain relievers can help alleviate some of the pain.


Headaches, and in some cases dizziness or fainting, can be a side effect of both the shot and the nasal spray. This is considered a mild side effect, and it should not last longer than a day or two. If you are prone to fainting or dizziness with shots, be sure to inform your healthcare provider.


A fever of 101 degrees or less is a common side effect of both the shot and the nasal spray. A slight fever is considered a mild side effect, and it should go away within a day or two. A high fever (over 101 degrees) is not common, and you should call your doctor or seek medical attention if you are concerned.

Learn about possible complications from the flu »

Runny Nose and Sore Throat

The nasal spray can cause a few side effects that the shot does not. This is because of where the nasal spray is administered. Some people who receive the nasal spray experience a runny nose and sore throat afterwards.

Severe Allergic Reactions

Rarely, the flu vaccine can cause severe allergic reactions. The signs of a severe allergic reaction include hives, swelling, trouble breathing, an accelerated heartbeat, changes in behavior, dizziness, and weakness. Severe allergic reactions usually happen within a few hours of receiving the vaccine. If you experience any of these side effects, call 911 or your doctor immediately.

Guillain-Barré Syndrome (GBS)

In extremely rare cases, some types of flu vaccines can cause Guillain-Barré syndrome (GBS). This is a neurologic condition that causes weakness and paralysis throughout your body. This condition requires immediate hospitalization. Patients usually recover within a short amount of time. According to the Centers for Disease Control and Prevention, One in 100,000 people who received the swine flu vaccine in 1976 were at risk of developing GBS.

When Not to Take the Shot

Talk to your healthcare provider about the benefits and risks of getting the flu vaccine. While there are many side effects, most are mild and the severe side effects are very rare. You should avoid the vaccine if you are allergic to chicken eggs (the vaccine is made in chicken eggs), if you have had a severe reaction or Guillain-Barré syndrome in the past, or if you are suffering from a mild illness.

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