Young adults that received the Pfizer’s or Moderna’s second shot of the COVID vaccine were reported to have more heart inflammation than expected.

Cases of myocarditis or pericarditis were reported in the young adults.

U.S. health officials are investigating a higher-than-expected reporting’s of heart inflammation in male teens and young adults after their second dose of the Pfizer and Moderna vaccines.

As of May 31, the CDC agency had 275 preliminary reports of inflammation in 16- to 24-year-olds, CDC’s Dr. Tom Shimabukuro said in  a government vaccine meeting on Thursday. “That’s out of more than 12 million second-dose injections of the vaccines.”

However, it is still unclear if the heart inflammation is caused by the shots. The reports are currently rare according to the Centers for Disease Control and Prevention. It recommends everyone 12 and older to get vaccinated.

The CDC’s vaccine advisory committee meets on June 18 to further evaluate the possible risk.