FDA expands warning about rare heart side effect in two leading Covid vaccines

The Food and Drug Administration has mandated that Pfizer and Moderna expand warning labels on their mRNA COVID-19 vaccines (Comirnaty and Spikevax) to highlight a rare risk of myocarditis and pericarditis, which are heart inflammation conditions, primarily in males aged 16–25. The updated labels now cite an incidence rate of 38 cases per million doses in this demographic, up from prior warnings focused on ages 12–17 (Pfizer) and 18–24 (Moderna).

For all recipients under 65, the overall risk remains low at nearly 8 cases per million doses. This move follows FDA analysis of 2023–2024 vaccine safety data, including insurance claims and a study showing persistent cardiac MRI abnormalities in some patients five months post-diagnosis. The CDC, however, maintains that such cases are rare, typically resolve quickly, and are less severe than those caused by COVID-19 infection itself.

Policy clash and political tensions underpin new warnings

The FDA’s decision conflicts with prior CDC assessments that found no increased myocarditis risk in vaccine injury databases since 2022. It also aligns with broader efforts by Health Secretary Robert F. Kennedy Jr.’s administration to tighten vaccine oversight. Kennedy recently replaced all 17 CDC advisory panel members with appointees, including anti-vaccine advocates, and FDA Commissioner Marty Makary, a critic of COVID-19 booster mandates, has restricted annual shots to high-risk groups (e.g., senior citizens).

Critics argue the label expansion overlooks context: Studies confirm COVID-19 infection poses a 16-fold higher myocarditis risk than vaccination, and most post-vaccine cases are mild, resolving with anti-inflammatory treatment. Yale researchers note the inflammation is transient, not autoimmune, allowing full recovery.

Expert backlash and global safety perspectives

Medical experts condemn the FDA’s approach as misleading. “They are right to suggest that we need to consider myocarditis risks associated with the vaccine, but what they propose is exactly the wrong solution,” said Dr. Robert Morris of the University of Washington. “We should be investigating who is prone to myocarditis to see if we can predict and mitigate that risk," according to a report by AP.