Doctors offered reassurance Tuesday following several dozen reports of mostly mild heart problems after Covid-19 vaccinations, but suggested recipients and their families pay close attention to possible symptoms, such as chest pain and shortness of breath.
It remains unclear whether the vaccine is the cause of the heart problem, called myocarditis. Last week, the Centers for Disease Control and Prevention's vaccine safety group said it was looking into "relatively few reports" of the condition in vaccinated individuals — primarily teenagers and young adults.
The CDC did not respond to questions about the exact number of reports. However, NBC News identified at least 55 suspected cases nationwide.
That number includes 14 cases under investigation by the Department of Defense among members of the military, but it may be an underestimate. And some, but not all, state departments of health are tracking such cases.
The Connecticut Department of Public Health said 18 cases in teenagers or young adults have been reported in that state. As of Tuesday, all but one had been released from the hospital and are "doing fine," Dr. Deidre Gifford, acting commissioner for the Connecticut DPH, said during a news conference earlier this week.
Seven cases have been reported to the New York State Department of Health, three cases are under investigation in Idaho, and six have been reported in Oregon. The Colorado Department of Public Health & Environment has received four reports.
"In recent weeks, there have been rare reports of myocarditis and pericarditis occurring after Covid-19 vaccination in the United States and Europe," the CDC said in a statement. "Reported cases appear to be mild and often go away without requiring treatment."
Myocarditis and pericarditis are conditions that involve inflammation in and around the heart.
Cases have been reported more often in males than in females, according to the CDC. The onset occurs more often following the second dose, typically within four days of receiving that shot.
The agency is coordinating its investigation with the Food and Drug Administration, which authorized the vaccines for emergency use.