The Food and Drug Administration has updated its warning labels for the Pfizer and Moderna COVID-19 vaccines, expanding information about a rare but potential heart-related side effect.

The updated guidance highlights myocarditis and pericarditis, two types of heart inflammation, as possible adverse events following vaccination with mRNA-based shots. The FDA cites new findings from a study that detected abnormal heart scans suggesting potential heart injury that could last for months after vaccination.

However, the agency emphasizes that these cases remain extremely rare, occurring in approximately 8 out of every 1 million vaccine recipients. The warning also notes that the overall significance of the findings remains unknown and continues to be studied.

The expanded label applies to both the Pfizer-BioNTech and Moderna COVID-19 vaccines.

Health officials continue to recommend vaccination, stating that the benefits outweigh the risks, especially in preventing severe illness and death from COVID-19.