Officials with the Centers for Disease Control and Prevention (CDC) will hold an emergency meeting this week to discuss reports of heart inflammation related to some COVID-19 vaccines.

The agency on Thursday identified 226 of 475 case reports that meet the agency’s “working case definition” of myocarditis and pericarditis —two types of heart inflammation in people under 30 after the mRNA-based Pfizer and Moderna vaccines.

In total, 285 case reports from the CDC’s Vaccine Adverse Event Reporting System showed disposition towards the conditions. Of those cases, 270 had been been discharged, and 15 remained hospitalized — three of whom were in intensive care, according to the report from the federal government.

The preliminary results, as of May 31, found the cases predominantly in male patients of younger age groups (16-24), particularly after their second dose, according to the report. Pfizer is the only vaccine currently authorized for the youngest ages groups.