The United States' Food and Drug Administration (FDA) alerted everyone that there might be rare risk of heart inflammation in youth who had received both doses of the mRNA COVID-19 vaccine.
The fact sheets have been revised for each vaccine which includes a warning that reports of adverse events suggest increased risks of myocarditis and pericarditis, particularly after the second dose and with the onset of symptoms within a few days after vaccination.
According to FDA, till June 11, over 1,200 cases of myocarditis or pericarditis have been reported to the US Vaccine Adverse Event Reporting System (VAERS), out of about 300 million mRNA vaccine doses administered.
The investigation revealed that cases were higher in men and in the week after the second vaccine dose. 309 people were hospitalised from heart inflammation in persons under the age of 30, of which 295 have been discharged.
Health regulators in different countries were probing cases of myocarditis and pericarditis. These cases are more frequently found in young men after getting the Pfizer or Moderna shots, vaccines that are based on the mRNA technology.