The US Food and Drug Administration Friday added a warning about the risk of heart inflammation to fact sheets for Moderna and Pfizer-BioNTech COVID-19 vaccines.

The warning noted that reports of adverse events following vaccination, particularly after the second dose, suggest increase risks of myocarditis, or inflammation of the heart muscle, and pericarditis, or inflammation of the tissue surrounding the heart.

The warning update follows an extensive review of information and the discussion by CDC's Advisory Committee on Immunization Practices meeting on Wednesday, the FDA said.

At the end of second-week of June, more than 1,200 cases of myocarditis or pericarditis have been reported to the US Vaccine Adverse Event Reporting System.

The cases reported appear to be notably higher in males and in the week after the second vaccine dose.