Dr. Rochelle Walensky, Directors of the U.S. Centers for Disease Control and Prevention (CDC) said Thursday that more than 300 young individuals reported heart inflammation after COVID-19 vaccination, according to NBC News.

She said, “The cases are rare. Over 20 million adolescents and young adults [have been] vaccinated in the United States.”

The number of cases of heart inflammation, either myocarditis or pericarditis, is still higher than what would be expected for this age group.

With a growing number of these cases, the CDC is planning a meeting of a panel of independent experts called the Advisory Committee on Immunization Practices. The members will gather today to review the cases.

The panel will discuss the recent research and safety data on myocarditis following vaccination; however, it will not make any changes to the current COVID-19 vaccination guidelines.

So far, the United States has approved only the Pfizer-BioNTech vaccine for children aged 12 and above, though young adults 18 and above can receive either Pfizer-BioNTech, Moderna, or Johnson & Johnson’s vaccines.

The CDC said it remains unclear whether the vaccines are directly responsible for causing heart issues, but the agency said there is growing evidence for the link.

Dr. Paul Offit, a pediatrician specializing in infectious diseases, vaccines, immunology, and virology, said the panel’s meeting should “clear understanding of the current risks for either children or young adults” from the vaccine.

Dr. Walensky said the CDC has asked “clinicians to be on the lookout for and report patients with symptoms of myocarditis or pericarditis following vaccination.”

Signs and symptoms of myocarditis or pericarditis can include fever, fatigue, shortness of breath, and chest pain.

Most of the cases reported have not been serious. The CDC director said, “The vast majority have fully resolved with rest and supportive care.”

Dr. Katie Passaretti, Medical Director, Atrium Health in Charlotte, said, “People who have had this side effect tend to have had mild or minimal symptoms that resolve within several days.”

Today’s meeting “is yet another demonstration of our ongoing efforts to keep safety central in everything we do,” Dr. Walensky said. “Getting vaccinated is our way out of this pandemic.” This story appeared on NBC News and Today.