A Centers for Disease Control and Prevention panel is meeting Wednesday to discuss whether certain COVID-19 vaccines are linked to a heart problem in teens and young adults.

The agency is investigating a possible spike in cases of heart inflammation after people in those age groups got their second dose of the Pfizer of Moderna vaccine.

The CDC has said cases are rare and most have already fully recovered.

Earlier this month, an article on seven U.S. teen boys in several states was published in Pediatrics. The boys, aged 14 to 19, received Pfizer shots in April or May and developed chest pain within a few days. Heart imaging tests showed a type of heart muscle inflammation called myocarditis.

The CDC says there have been more than 1,200 cases of myocarditis, mostly in people under 30 years old who received the Pfizer or Moderna vaccine. The CDC says it is rare, but it is higher than what would be expected for the under 30 age group.

The data shows that out of 300 million doses there has been about 1,200 cases of myocarditis in 12 to 30 year olds but it was slightly higher in 12 to 17 year olds.

Only one of the seven boys in the Pediatrics report had evidence of a possible previous COVID-19 infection and doctors determined none of them had a rare inflammatory condition linked with the coronavirus.

A Pediatrics editorial noted that among U.S. children under age 18, there have been over 4 million COVID-19 cases, more than 15,000 hospitalizations and at least 300 deaths.

The CDC says the condition is rare and is still advising people to get the vaccine. They say anyone who experiences chest pain, shortness of breath or rapid heartbeat within a week of being vaccinated should seek medical attention.