Pfizer, Moderna Vaccines Possibly Linked to Rare Heart Inflammation: European Drug Regulator

The European Medicines Agency (EMA) warned Friday that COVID-19 vaccines by Pfizer and Moderna are possibly linked to rare heart inflammation conditions, but emphasized that the benefits of being vaccinated continue to outweigh the risks.

The EMA said the heart conditions, myocarditis and pericarditis, must now be listed as side effects of the two mRNA vaccines, following an analysis of over 300 cases found in vaccinated individuals.

Myocarditis is inflammation of the heart muscle and pericarditis is the inflammation of the lining around the heart. Symptoms of both include chest pain, palpitations and shortness of breath.

In total, the European drug regulator reviewed more than 321 cases of myocarditis and pericarditis found in the European Union, Iceland, Norway and Liechtenstein. Of those, the agency analyzed 145 cases of myocarditis and 138 cases of pericarditis linked to the BioNTech/Pfizer vaccine, and 19 cases of each condition linked to the Moderna vaccine, Politico reported.

The study found that the heart conditions mostly occurred within 14 days of inoculation and typically affected younger men. Most of the cases occurred after inoculation with Pfizer's vaccine, the agency said, while noting that Pfizer's vaccine has been used more widely across Europe than Moderna's.

In response to the findings, Pfizer said in a statement that the cases were "generally mild" and individuals "tend to recover within a short time following standard treatment and rest."

Newsweek contacted Moderna for additional comment.

The EMA added Friday that individuals and healthcare professionals should be aware of the possible vaccine side-effects, but said that the benefits of being vaccinated "continue to outweigh their risks," Reuters reported.

Europe's drug regulator said Friday that Pfizer and Moderna vaccines are possibly linked to a rare heart inflammation condition. Here, Syringes wand vials of the Pfizer vaccine are prepared to be administered at a drive up vaccination site from Renown Health in Reno, Nevada on December 17, 2020. PATRICK T. FALLON/AFP/Getty Images

The agency had also been looking into such cases of the heart conditions linked to the Johnson & Johnson (J&J) and AstraZeneca vaccines, but on Friday said it had not found any causal relationship.

The EMA's findings correlate with a U.S. Centers for Disease Control and Prevention (CDC) study in June, which found over 1,200 cases of the heart conditions in those aged 16 to 24 who received Pfizer or Moderna. Among those individuals, men under 30 appeared to make up the bulk of reported cases.

According to the CDC findings, 79 percent of those who developed the heart conditions have fully recovered, and only 3 percent required hospitalization.

"Early data of acute outcomes of myocarditis after mRNA vaccines has been good," the CDC said in June. "There's typically quick resolution, there's obviously exceptions in all things but we are continuing to follow patients long term. We don't have long-term data available yet."

Updated 1:17 PM ET, to indicate Newsweek reached out to Moderna,