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Side Effects of Pfizer’s COVID-19 Vaccine in Children

What your kids and grandkids ages 5 to 11 can expect after they roll up their sleeves

spinner image A nine year old girl holds the sleeve of her top as she receives the COVID-19 vaccine.
MediaNews Group/Orange County Register via Getty Images

About 28 million children ages 5 to 11 are now eligible for a COVID-19 vaccine from Pfizer-BioNTech, nearly a year after the shots became available to older adults. And as parents and grandparents begin signing their young ones up for it, many are wondering what to expect.

Here’s what we know so far about the vaccine side effects in 5- to 11-year-olds.

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Side effects are similar across all age groups  

The good news is, there’s nothing new or different about the vaccine’s side effects in the younger population. And if anything, the few thousand children who participated in the clinical trials and received Pfizer’s two-shot, small-dose regimen — it’s one-third the dose given to individuals 12 and older — experienced fewer symptoms than vaccinated adolescents and adults. What’s more, no serious safety concerns were observed in the study.

Top 5 Side Effects Seen in Kids Ages 5 to 11 

The most common side effects after the second dose of Pfizer’s 10-microgram COVID vaccine in clinical trials for children ages 5-11.

  1. Injection site pain
  2. Fatigue
  3. Headache
  4. Muscle pain
  5. Chills

Source: CDC/Pfizer-BioNTech

Pain at the injection site was the most common complaint, according to study data presented to the Centers for Disease Control and Prevention’s (CDC) advisory committee, with about 70 percent of kids in the 5-to-11 age group reporting it after each vaccine dose. Nearly 40 percent of the trial participants experienced fatigue after the second shot, about 28 percent had a headache, around 12 percent had muscle pain and about 10 percent reported chills.

Not only are these “self-limiting” side effects similar to those seen in adults who got the COVID vaccine, CDC Director Rochelle Walensky said in a recent press briefing, but they’re comparable to the symptoms that occur with “other vaccines recommended for children,” including tetanus, diphtheria and pertussis (Tdap) and the flu vaccine.

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Tips for treating symptoms  

When it comes to treating the side effects, pediatrician and vaccine researcher Robert Jacobson, of the Mayo Clinic, recommends not taking any medication until after the shot.

“When we used to give blanket recommendations of acetaminophen and ibuprofen before any injection, we noticed, at a population level, a dampening of the antibody response, which is worrisome. We don't want to tweak or adjust everybody's antibody response a little lower,” he told reporters in a recent media briefing.  

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Instead, wait until symptoms, if any, set in. Acetaminophen or ibuprofen can help with body aches, headaches and fever, Jacobson says; ice packs can ease the pain of a sore arm. And never underestimate the power of a nap, which can also help little ones feel better.  

“One thing I recommend you don't do after the injection site soreness is to rub or massage it,” he adds. “It turns out rubbing or massaging the injection site actually worsens the pain and can make it more problematic.”

What to know about myocarditis risks

Health experts are keeping a close eye on myocarditis, or inflammation of the heart muscle brought on by the body’s own immune system, which is a rare reaction that has been seen in a small share of Pfizer and Moderna vaccine recipients, mostly male adolescents and young male adults. (There have been fewer than 1,000 CDC-confirmed cases.)

There are many causes of myocarditis: Viral infections, including a coronavirus infection, can trigger the condition; so can certain medications and some autoimmune disorders. And vaccines, while an uncommon culprit, can sometimes lead to myocarditis.

Most of the myocarditis cases reported after COVID-19 vaccination have been temporary and mild to moderate in nature, meaning patients were able to recover on their own or with some medical treatment. The outcomes brought on by COVID infection, however, have been more consequential.

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While children tend to fare better than adults, they are not immune to illness caused by a coronavirus infection. There have been more than 8,300 COVID-related hospitalizations among 5- to 11-year-olds since the start of the pandemic, the CDC’s Walensky said, and more than 5,000 have suffered from a life-threatening COVID-related condition called multisystem inflammatory syndrome (MIS-C), which can cause inflammation in the heart, lung, kidneys and brain, as well as other organs. Kids ages 5 to 11 account for nearly 45 percent of these cases.

About 800 children under 18 have died from COVID, according to federal data; 173 have been between the ages of 5 and 11.

The delta variant has made things considerably worse. During a six-week period from late June to mid-August, COVID-19 hospitalizations among children and adolescents increased fivefold, according to CDC data. In the clinical trials, Pfizer’s vaccine was found to be about 91 percent effective at preventing COVID-19 among children ages 5 to 11 — even with delta in the mix.

“The numbers of what you prevent [when it comes to COVID-19 cases, hospitalizations and deaths] with the vaccine far outweigh the small risks of mild to moderate and temporary myocarditis or muscle inflammation,” Jacobson says. Modeling done by the U.S. Food and Drug Administration (FDA) also show that, overall, the benefits of the vaccine outweigh any risks.

It’s possible that myocarditis will be even rarer in the 5 to 11 age group, some experts predict. One reason: The vaccine is a smaller dose than those administered to adolescents. Another: The condition occurs most often in young adults, according to the National Heart, Lung and Blood Institute — not young kids.  

“I think most of us should feel very confident that the risk of myocarditis is going to be much, much lower in this [5 to 11] population,” Ashish Jha, M.D., dean of Brown University’s School of Public Health, noted in a recent media briefing.

Prepping children for the vaccine

Most adults don’t exactly love getting stuck with a needle, and kids have their own fears when it comes to shots. But Jacobson has some tips on how to ease the stress of it all. 

First, don’t surprise your child or grandchild with a vaccine appointment; talk to them about getting their COVID shot a few days ahead of time. “The child should not first be hearing about the vaccine when they show up at a provider's office or at a pharmacy,” Jacobson says.

Second, let young kids know that the pain from the needle is temporary, but the effect of the vaccine and the protection it affords is longer lasting. And finally, serve as an example by getting your COVID vaccine and staying up to date on other vaccinations.  

“These are all things that you can do to prepare your child for the COVID-19 vaccination as well as other vaccinations that the child will be due for,” Jacobson says.

U.S. Surgeon General Explains Why Kids Should Be Vaccinated

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