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Flu Shot Reactions and Flu Shot Side Effects

Expert Q&A

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Updated November 01, 2012

Q. My toddler got a flu shot for the first time yesterday and now has a fever and is fussy. Is that from the flu shot? Diane, Phoenix, Arizona

A. In general, most kids tolerate their flu shots very well and many things inappropriately get blamed on flu shot reactions. For example, we have all heard of people who claim that they get the flu every time they get a flu shot, which isn't possible, since the flu shot isn't a live vaccine.

The Flumist nasal spray flu vaccine is made from a live vaccine, but it is made from weakened viruses and does not cause the flu.

Flu Shot Side Effects

Even though it won't cause the flu, flu shots can commonly cause mild side effects, especially in younger children who are getting their flu shots for the first time. These reactions and flu shot side effects can include:
  • Local Flu Shot Reactions, such as soreness, pain, and swelling where the flu shot was given, but which are usually mild and last for less than 2 days.

  • Systemic Flu Shot Reactions, which usually begin 6 to 12 hours after getting the flu shot, last for only 1 or 2 days, and can include fever, rash, malaise (not feeling good), and muscle aches.

  • Allergic Reactions, including hives, angioedema, and anaphylaxis, which can be life-threatening, but fortunately are rare, and can triggered by residual egg proteins in people allergic to eggs or to other components of the flu shot. Keep in mind that there are protocols that allow people with egg allergies to get flu shots, so talk to your doctor or allergist if your child is at high risk for complications from the flu and also has an egg allergy.

Flu Shot Reactions

Since this was your child's first flu shot and the fever and fussiness started right away, it could definitely be a flu shot side effect. Fortunately, this usually only lasts a day or two, so your child should quickly be feeling better. And it since this often is more common the first time you get a flu shot, you don't have to expect the same side effects when she gets a flu shot next year or with her second flu shot.

Even if it seems like her fever is from the flu shot, you should still call your pediatrician, especially if her fever is hard to control, she seems very fussy and is not consolable, or is not quickly getting better.

If your child has a more serious flu shot reaction, be sure to talk to your doctor before getting a flu shot in the future.

Flu Vaccine Reactions

Instead of a flu shot, more and more kids are getting Flumist, the nasal spray flu vaccine.

Flu vaccine reactions after Flumist can include:

  • runny nose or nasal congestion
  • low grade fever
  • headache
  • sore throat
  • muscle aches

Other flu vaccine reactions after Flumist might include sore throat, tiredness/weakness, cough, chills, and sinusitis.

One study also showed an increased rate of wheezing for younger children after getting Flumist, which is why children usually shouldn't get Flumist if they have had an episode of wheezing in the past 12 months. They should get a flu shot instead.

Or Is It Just A Coincidence?

Don't always be too quick to blame your flu shot if your child gets sick right away after getting a flu shot though. It could just be coincidence, especially if your child was already a little sick or is in daycare or around other sick kids.

Some things to consider when trying to figure out if a symptom is from the flu shot or from another illness:

  • Has your child had a flu shot before? If your child has had a flu shot several times before and never had a flu shot reaction, then it is less likely that your child's current symptoms are being caused by a side effect of the flu shot. In that case, it may just be a coincidence and she may just have a cold or other illness, especially when you remember that flu shots are given right at the beginning of cold and flu season.

  • How quickly after the flu shot did your child begin to have symptoms? Flu shot symptoms usually begin right away or within 6 to 12 hours, so if your child didn't get his fever until 2 or 3 days after getting a flu shot, then it probably wasn't from the flu shot.

  • What other symptoms does your child have? If your child already had a runny nose and cough for a week and then gets a flu shot and develops a fever, then it may just be that he developed a sinus infection and it may have nothing to do with the flu shot at all. That's a good reason to wait until your child is well before getting a flu shot, although sometimes you just have to get one when you can.

  • Is anyone else sick? If your child gets a flu shot and quickly gets a fever and sore throat, while it may be from the flu shot, if everyone around him has strep throat, you should likely get a strep test before simply trying to blame the flu shot.

  • How long has your child been sick? Remember that most flu shot reactions only last a few days, so if your child has a fever for more than a few days, then it may not be a flu shot reaction and you should see your pediatrician.
The main thing to remember is that just because two things happen at about the same time doesn't mean that one caused the other. For example, if you got your flu shot and bought a winning lottery ticket on the way home from your doctor's office, it doesn't mean that the flu shot made you lucky. They are two independent events and had no causal effect on each other.

Of course, if your child has the same reaction each and every time he gets a flu shot, then it probably is from the flu shot, no matter how many people tell you that it is a coincidence.

Flu Vaccine 2012

The 2012-13 flu vaccine will likely have similar seasonal flu vaccine side effects we see every other year, including:

  • mild fever
  • muscle aches
  • nausea
  • headache
  • soreness, redness, or swelling at the injection site (flu shot)
  • runny nose or congestion (nasal spray flu vaccine)

Reporting Flu Shot Reactions

As with other vaccine reactions, either a parent or a doctor can report possible side effects and reactions from flu shots to the Vaccine Adverse Event Reporting System (VAERS), a 'post-marketing safety surveillance program' that is maintained by the FDA and CDC.



Sources:

CDC. Seasonal Influenza Vaccine Safety: A Summary for Clinicians. http://www.cdc.gov/flu/professionals/vaccination/vaccine_safety.htm. Accessed October 2010.

CDC. Prevention and Control of Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices (ACIP), 2012-13 Influenza Season. MMWR. August 17, 2012 / 61(32);613-618

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