Side Effects of the Flu Shot in Kids

flu shot side effects

Illustration by Cindy Chung, Verywell

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By and large, kids tolerate flu shots well, but some may experience side effects that are typically brief and mild. The benefits of the flu shot far outweigh any discomfort a person may experience. This is especially true for young children who can develop serious complications if they catch influenza.

Myths About the Flu Vaccine

There have long been myths and misconceptions about the flu shot, especially when it comes to young children and toddlers. One of the most common is that it causes the flu, an impossibility since the vaccine is not made with a live virus.

Even when the vaccine is delivered with the FluMist nasal spray (which is a live vaccine), it is created from a weakened form of the virus which is unable to cause the flu.

The flu shot does not cause the flu. Side effects may occur, but they are rare and the risks of these side effects are outweighed by the benefits that this preventative measure provides.

Common Side Effects

There is no side-stepping the fact that flu shots can cause side effects, especially in younger children who may be getting their shots for the first time. Most typically last a day or two, and they are almost always mild.

Possible flu shot reactions may include:

  • Fatigue
  • Headache
  • Low-grade fever
  • Muscle aches
  • Nausea
  • Pain and swelling at the injection site

If any side effect seems concerning to you, follow your instincts and call your pediatrician. In the event of fever, do not use aspirin as this can cause a rare but serious condition in children called Reye's syndrome, an illness characterized by the swelling of the liver and brain.

While rare, allergic reactions can sometimes occur, including potentially life-threatening anaphylaxis. If there is facial swelling, breathing difficulty, vomiting, hives, dizziness, rapid pulse, or fainting, call 911 or go to your nearest emergency room immediately. 

Common Flu Nasal Spray Reactions

To avoid needles, some parents opt for the FluMist nasal spray for their child. Introduced in 2003, the FluMist vaccine is approved for use in people age 2 to 49. However, it is not used during flu seasons when it doesn't contain the strains of influenza that are predicted to be circulating that year.

While fast and easy to administer, the spray does have a number of possible side effects, such as:

  • Cough or a sore throat
  • General malaise
  • Headache
  • Low-grade fever
  • Muscle aches
  • Nasal congestion
  • Runny nose

Children should not be given the FluMist vaccine if they are allergic to eggs or gelatin. As with the flu shot, neither children nor teens should be given aspirin to treat fever.

Symptoms vs. Side Effects

If your child feels unwell after getting the flu vaccine, it is understandable to assume that it was related to the shot. However, it may just be a coincidence, especially if your child is in daycare or around other sick children.

It is important to differentiate this because some parents will attribute a symptom or illness to the flu shot and swear to never use it again. This would increase the risk of the child catching influenza and developing a serious complication. Before drawing a conclusion, ask yourself a few questions:

  • Has your child had the flu shot before? If your child has had one before without a reaction, it is unlikely the symptoms caused by the vaccine.
  • How long has your child been sick? If a symptom persists for more than 2 days or worsens, it is unlikely that the flu shot is the cause. In such a case, it's best to see your pediatrician as soon as possible.
  • Is anyone else sick? If your child gets sick after the flu shot (as opposed to feeling unwell or tired), find out if other parents have experienced the same with their kids. This is especially true in your child is in daycare where viruses are readily passed from one toddler to the next.
  • What other symptoms does your child have? Since the symptoms of a flu shot are pretty non-specific, any number of things may have caused them. If an isolated symptom appears, such as nasal congestion, ask yourself if there any other possible cause for this (such as hay fever or a developing cold).
  • When did the symptoms begin? Flu shot symptoms usually appear within 6 to 12 hours. If an illness appears 2 to 3 days after getting the shot, it is probably unrelated.

In the unlikely event your child has the same reaction year after year, then it is probably not a coincidence. You may need to avoid the flu shot and speak with your pediatrician about using FluMist as an alternative.

You should also report the reaction to the Vaccine Adverse Event Report System, a safety surveillance program managed by the U.S. Food and Drug Administration and the Centers for Disease Control and Prevention.

1 Source
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  1. U.S. Food and Drug Administration. FDA information regarding FluMist Quadrivalent Vaccine.

Additional Reading

By Vincent Iannelli, MD
Vincent Iannelli, MD, is a board-certified pediatrician and fellow of the American Academy of Pediatrics. Dr. Iannelli has cared for children for more than 20 years.