Flu Vaccine Side Effects in Kids

The influenza shot can cause mild side effects in children and toddlers, but they shouldn’t deter your family from getting vaccinated. Here’s what experts have to say.

Influenza season is typically between fall and spring every year, peaking between December and February most seasons. Flu season trends may be different every year, but for the 2022-2023 flu season, the Centers for Disease Control and Prevention (CDC) predicts that there may be as many as 14 million flu illnesses and up to over 8,000 flu-related deaths. Anyone can experience severe cases of the flu, but children younger than 5 years old may be especially at risk for developing pneumonia, dehydration, and other complications.

Getting the flu shot is the best way to protect your family. The vaccine reduces your risk of flu illness by 40 to 60%, and it also decreases the severity of symptoms if you do happen to contract influenza. The CDC recommends that everyone 6 months and older get vaccinated each year, ideally in September or early October to get full protection before flu season hits. And while every vaccination may come with potential side effects, it's important for parents to know that overall, the benefits of the flu shot outweigh any potential side effects that may arise.

"The side effects (of the flu shot) are about as minimal as the side effects for any vaccine," explains Amina Ahmed, M.D., FAPP, a hospital epidemiologist and professor of infectious disease at Atrium Health's Levine Children's Hospital. Keep reading to learn more about the side effects of the flu shot and nasal spray vaccine, and why they shouldn't prevent your family from getting vaccinated.

doctor giving patient in pediatrician's office vaccination
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Flu Shot Side Effects for Children and Toddlers

The flu shot is made with an inactivated (dead) flu virus, so it can't give you influenza, says Daisy Dodd, M.D., a pediatric infectious disease doctor for Kaiser Permanente in Southern California. Even so, people can have minor side effects after receiving the shot. Child and toddler flu shot side effects include:

  • Soreness, redness, or discomfort in the injection site. This localized reaction is the most common side effect, says Dr. Ahmed.
  • Body aches
  • Low-grade fever
  • Headache. "This can usually be alleviated by taking pain medication like Tylenol, but in my opinion, it's very minor," adds Dr. Dodd.
  • Nausea
  • Fatigue
  • Fainting in rare cases

These side effects generally last between one and two days. "The most common reactions people have to flu vaccines are considerably less severe than the symptoms caused by actual flu illness," stresses the CDC.

Side Effects of the Nasal Spray Flu Vaccine

When it comes to flu vaccines, shots aren't the only option. Some people receive the live attenuated flu vaccine (nasal spray) instead of the shot. A lifesaver for those who hate needles, this vaccine is only given to those over 2 years old who don't have asthma, diabetes, or other health issues that compromise the immune system. That's because it contains the live flu virus—but in such weakened quantities that it can't cause a full-blown flu, says Dr. Ahmed.

Side effects of the nasal spray flu vaccine include:

  • Congestion
  • Runny nose
  • Headache
  • Wheezing
  • Vomiting
  • Sore throat
  • Low-grade fever
  • Cough

Are Severe Flu Vaccine Side Effects Possible?

It's unusual to have serious side effects from the flu shot. Life-threatening anaphylactic reactions (usually due to egg protein in the vaccine) are also rare, and "the new vaccines are actually very safe for those with egg allergies," says Dr. Dodd. Symptoms of an allergic reaction show up within minutes to hours, according to the CDC, and they include breathing trouble, weakness, fast heart rate, dizziness, hives, sweating, hoarseness, and paleness. Find emergency assistance immediately if you suspect an allergic reaction from the flu vaccine.

What's more, the flu shot may have a small association with a rare disorder called Guillain-Barré syndrome (GBS), in which the immune system attacks your nerves. Some studies found that GBS occurs fewer than 1 or 2 times out of every one million vaccinations; others didn't find any link, says the CDC. It's important to note, though, that GBS may also occur after getting the flu. In fact, "you have a greater chance of getting GBS from influenza than by the vaccine itself," says Dr. Dodd, adding that it's still highly unlikely.

The Bottom Line

The flu shot may cause minor side effects in toddlers and children, but the benefits of vaccination vastly outweigh the risks.

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