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The Oregon Health Authority said it was aware of at least 11 cases of myocarditis or pericarditis — inflammation of the sac surrounding the heart — in all age groups following COVID vaccination, according to The Oregonian.

One of the cases is a 15-year-old teen in Beaverton, Oregon, who was hospitalized for heart inflammation after receiving his second dose of the Pfizer vaccine.

The teen, who requested his name not be used to protect his privacy, said he started feeling some of the more common side effects of the vaccine, such as fever and lack of appetite, one day after being vaccinated. He also told his mother his heart hurt and felt as if it were being squeezed.

“I didn’t really catch that,” his mother said, though she said she’s been reading COVID news obsessively for months and was aware of some of the early reports on heart problems in children following vaccinations. “I thought he was joking.”

When the teen woke up the following morning and the pain was still there, his parents took him to Providence St. Vincent Medical Center, where scans confirmed he had myocarditis.

Myocarditis is inflammation of the heart muscle that can lead to cardiac arrhythmia and death. According to researchers at the National Organization for Rare Disorders, myocarditis can result from infections, but “more commonly the myocarditis is a result of the body’s immune reaction to the initial heart damage.”

“The hallmark symptom of myocarditis and pericarditis is chest pain or shortness of breath,” Jonathan Modie, an Oregon Health Authority spokesperson, said in an email. “In rare cases, it can also present in the form of heart palpitations. Anyone suffering from unexplained chest pain should contact a medical provider or seek immediate emergency care.”

Public health officials and specialists said chest pain is atypical in pediatric patients, but myocarditis can be a side effect from other vaccinations, viral infections, drug use or toxins in the system.

Dr. Genevieve Buser, a pediatric infectious disease specialist at Providence St. Vincent, said the case rate of myocarditis potentially connected to COVID vaccinations is still below the background rate in that age group from other causes.

However, as The Defender reported today, the Centers for Disease Control and Prevention now acknowledges a higher risk of myocarditis and pericarditis in 16- to 24-year-olds vaccinated with mRNA vaccines, which includes the Pfizer and Moderna vaccines being administered in the U.S.

According to a statement, updated June 1, on the CDC website:

“Data from VAERS [Vaccine Adverse Events Reporting System] show that in the 30-day window following dose 2 mRNA COVID-19 vaccination, there was a higher number of observed than expected myocarditis/pericarditis cases in 16–24-year-olds.”

Last month, as The Defender reported, Connecticut health authorities reported 18 cases of heart problems among teens who received a COVID vaccine.

All 18 cases resulted in hospitalization — the vast majority for a couple of days, reported NBC Connecticut. The cases were reported to the Connecticut Department of Public Health by vaccine providers, according to Deirdre Gifford, acting health commissioner.

The latest data from the CDC’s Vaccine Adverse Events Reporting System (VAERS) showed 40 cases of heart inflammation in the 12-17 year adolescent age group reported after COVID vaccination — all associated with Pfizer.