(WJW) — The Centers for Disease Control and Prevention is investigating reports of a small number of younger coronavirus vaccine recipients who experienced heart problems after getting the shot.

According to a report from the agency’s vaccine safety group, several individuals had presentations of myocarditis.

Myocarditis is an inflammation of the heart muscle and can occur following certain infections, the Mayo Clinic reports.  This condition can also affect the heart’s electrical system, reducing the organ’s ability to pump. It can also cause rapid or abnormal heart rhythms.

The CDC says, to date, there are few reports of myocarditis post-vaccination and that the cases seemed to occur predominantly in adolescents and young adults. The cases were presented more often in males than females.

Data shows that myocarditis is found in patients more often following the second dose of the vaccine than the first and typically occurs within four days of vaccination.

Most cases appeared to be mild.

According to the New York Times, the CDC’s review of the reports of myocarditis is “in the early stages.” The news outlet says health experts have yet to determine if the condition has any connection to the coronavirus vaccine.

Dr. Celine Gounder, an infectious disease specialist at Bellevue Hospital Center in New York, told the New York Times it could simply be a “coincidence” that vaccinated individuals are developing the condition.

“It’s more likely for something like that to happen by chance, because so many people are getting vaccinated right now,” she reportedly said.

The CDC says they are continuing to investigate and follow-ups into the cases remain ongoing.