Information about myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the lining outside the heart) following vaccination with these mRNA COVID-19 vaccines has been included in the labeling since 2021. FDA closely monitors the safety of all vaccines, including the COVID-19 vaccines, during postmarket use.
About the Study on Cardiovascular Outcomes in mRNA COVID-19 Vaccine Recipients Diagnosed With Myocarditis
In a post-approval U.S. studyExternal Link Disclaimer funded and co-authored by FDA and published in September 2024, follow-up information was collected on approximately 300 people who developed myocarditis after receiving the original formula of an mRNA COVID-19 vaccine. Some people in the study reported having heart symptoms approximately 3 months after developing myocarditis. Some people in the study had cardiac MRIs (scans that show detailed images of the heart muscle) initially after developing myocarditis and again approximately 5 months later. The initial and follow-up cardiac MRIs commonly showed signs of injury to the heart muscle, with improvement over time in some but not all people. It is not known if these cardiac MRI findings might predict long-term heart effects of myocarditis.
