By Stephanie Stahl

PHILADELPHIA (CBS) — There are growing concerns that not enough children are getting the COVID vaccine. Only 35% of children 10 to 14 have received at least one dose.

And while most children hospitalized are not vaccinated, some have rare side effects from the vaccine.

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The virus and the vaccine can both cause an inflammation of the heart, but with the vaccine, it’s very rare and can be easily treated. A lesson one Philadelphia family is relieved to know.

“I’m feeling pretty fine, feeling normal,” Jack Sepe said.

Twelve-year-old Jack Sepe is getting ready to be released from CHOP.

“It was like chest pain and it really felt like a burning and it really, really hurt,” Sepe said.

The symptoms started the day after the Center City 7th grader received his Pfizer booster shot.

“Whenever your kids say, there’s something wrong with your kid’s heart that’s very scary,” mother Laura Sepe said.

Myocarditis can be caused by any kind of viral infection, including COVID-19, and there’s a slight risk it can be triggered by the vaccine.

“It is really a pretty rare occurrence,” Pediatrician Dr. Emmanuel Walter Jr. said. “With young adults and adolescents who have had myocarditis, it’s usually pretty mild. Lasting only a couple of days and is pretty easily treated with medications.”

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Myocarditis symptoms include chest pain, fatigue, irregular heartbeat, and shortness of breath.

“It happens more frequently in young men and adolescent boys,” Epidemiologist Dr. George Rutherford said.

Doctors say the benefits of the vaccine outweigh any risks.

“I’ve been told it’s much better that he got it from the vaccine than if he got this side effect from COVID itself,” Sepe said.

Jack’s mom is worried people will misinterpret her son’s case to falsely claim the vaccine isn’t safe.

“I would rather get the booster and have a really low chance of getting this than I would of getting COVID and being sick,” Jack said.

Now, with no lingering health issues, Jack gets to go back to school.

“I do have to go to school tomorrow,” Jack said.

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Doctors say it’s important for parents to get medical advice if children develop concerning symptoms after getting vaccinated. The same goes for adults who can also have the same complications.

Stephanie Stahl