When the Covid vaccine became available for more than 28 million children ages 5 to 11 across the nation in fall 2021, the news offered a sense of relief to some parents who had been waiting for this moment since the start of the pandemic so many long months ago. But for others, this news was mixed with hesitancy over fears of vaccine side effects, most notably, myocarditis, an inflammatory heart condition.

Kids aren't just tiny adults, meaning they can react differently to medications and vaccines, so it's understandable that some parents may be hesitant to vaccinate. However, the side effects of the Covid vaccine in kids are mild—and some kids may not even experience any side effects at all.

The Centers for Disease Control and Prevention (CDC) approval came after advisory panels to both the CDC and the Food and Drug Administration (FDA) overwhelmingly recommended the vaccine. After a rigorous data review, both agencies concluded that a universal vaccine for kids that prevents severe Covid greatly outweighs the potential side effects from receiving the shot. 

The Pfizer vaccine was found to be 90.7% effective in preventing symptoms of the virus and protecting against severe disease and the need for hospitalization. Side effects in this age group were also found to be more mild and less common than side effects in adolescents and adults. Though the trial was relatively small, no cases of myocarditis were seen in the Pfizer trials.

That’s most likely due to the smaller dosage of the pediatric vaccine, which is one-third of the dose of the vaccine for adults. Researchers identified this smaller dose as one that will still confer a strong immune response in kids—preventing severe disease and hospitalization—while minimizing potential side effects. (It's important to remember that the purpose of vaccination is not to prevent illness altogether, but to prevent severe disease.)

But at this point, still just 27.8% of kids in the 5 to 11 age group have been fully vaccinated, according to CDC data.

Related: Moderna will seek FDA authorization of its vaccine for kids ages 6 months to 6 years

What are the side effects of the Covid vaccine for kids?

The most common side effects seen in the 2,268 children observed in the Pfizer trials were mild. 

Common side effects:

  • Pain at injection site (upper arm)
  • Fatigue
  • Headache
  • Muscle pain
  • Joint pain
  • Fever
  • Chills
  • Swollen lymph nodes
  • Nausea
  • Decreased appetite

These side effects are typically temporary, clearing up within 48 hours. Most occurred after the second dose rather than the first (aside from arm soreness at the injection site).

According to data submitted to the FDA, 70% of children experienced pain at the injection site, 39% experienced fatigue, 28% experienced headaches and fewer than 10% of kids experienced muscle or joint pain, fever and chills.

There were no serious side effects reported. Just like with adults, your child will be monitored for 15 or 30 minutes after getting the shot in case any allergic reactions occur.

Related: Everything parents need to know about BA.2, the new Covid variant

How can I prevent side effects in my child?

The Mayo Clinic doesn't recommend giving an over-the-counter pain reliever to your child before vaccination.

However, it is OK to give your child a pain-reliever after they get a Covid vaccine—but talk to your doctor about this, too.

Related: Croup is now a symptom of Covid in kids

Is myocarditis a side effect of the pediatric Covid vaccine?

We know from Pfizer’s clinical trial data that there were no signs of a type of heart inflammation known as myocarditis observed. But there have been cases of myocarditis and pericarditis (another type of heart inflammation involving the heart muscle lining) reported several days after the second dose of an mRNA vaccine, primarily in men between the ages of 12 and 29

The CDC has since updated its guidelines for those ages 12 to 39 who are not otherwise immunocompromised to wait eight weeks between the first and second dose of mRNA vaccines to reduce the small risk of myocarditis even further.

The risk of myocarditis is higher after Covid infection

In truth, the risk of getting myocarditis from Covid infection is much greater than from a side effect of the vaccine, shares Preeti Parikh, MD, a pediatrician and medical director at GoodRx. The virus can infect the cardiac muscle and weaken the heart and surrounding blood vessels.

New research confirms this: In a study published in the Morbidity and Mortality Weekly Report, authors analyzed health records of more than 15 million people between January 2021 and January 2022, looking for occurrences of myocarditis and pericarditis after infection and after vaccination.

They found that cardiac issues were much higher after Covid infection than Covid vaccination.

Among males age 5 to 11, no cardiac issues were reported after the second dose. After Covid infection, the rate of cardiac issues was 93-133 out of every 100,000.

Among females ages 5 to 11, no cardiac issues were reported after the second dose, but 67-94 out of every 100,000 reported a heart issue after Covid infection.

For males ages 12 to 17, 27-36 out of every 100,000 reported an incidence of myocarditis or pericarditis after receiving the second dose, but 151-180 out of every 100,000 reported a heart issue after Covid infection, making the risk of cardiac issues 1.8 to 5.6 times more likely after infection than vaccination.

For females ages 12 to 17, 2-5 out of every 100,000 reported an incidence of myocarditis or pericarditis after receiving the second dose, but 63-93 out of every 100,000 reported a heart issue after Covid infection.

“These findings support continued use of recommended mRNA COVID-19 vaccines among all eligible persons aged ≥5 years,” the authors write.

While there is a very low risk of myocarditis from mRNA vaccines, it’s important to highlight the fact that myocarditis may resolve on its own, even without treatment. However, if your child has any symptoms of myocarditis (outlined below), seek medical care.

Symptoms of myocarditis

Potential signs and symptoms of myocarditis (inflammation of the heart muscle) or pericarditis (inflammation of the lining outside the heart):

  • Chest pain
  • Shortness of breath
  • Heart palpitations

If your child experiences any of the above symptoms, call your child’s doctor.

While no vaccine is 100% effective nor completely without side effects, both the FDA and CDC ultimately determined that mRNA vaccine benefits significantly outweigh the possible risk of vaccine side effects for kids ages 5 and up. If you have more questions about vaccine safety, talk to your pediatrician.