Moderna Shot May Cause Double To Triple As Many Heart Problems As Pfizer, New Study Finds

Moderna’s COVID-19 shot may cause two to three times as many heart-related side effects as Pfizer’s, according to a new Canadian study.

The rates of myocarditis and pericarditis in individuals within 21 days of getting their second shot were 35.6 and 22.9 per million doses, respectively, for Moderna compared to 12.6 and 9.4 per million for Pfizer, the research found. The connection between the mRNA vaccines and heart complications was most pronounced in men and younger vaccine recipients.

“in whom minimizing risk of myocardial insult is crucial, these data give a strong argument to preferentially use the BNT162b2 [Pfizer] vaccine over mRNA-1273 [Moderna]” https://t.co/70nNikSsSv

— Amesh Adalja (@AmeshAA) November 9, 2022

The study’s authors were quick to caution that incidences of heart inflammation were still fairly rare and that catching COVID-19 appears to carry a greater risk of myocarditis or pericarditis than receiving an mRNA vaccine.

Potential recipients should “consider the self-limiting and mild nature of most myocarditis events, benefits provided by vaccination, higher effectiveness of the Moderna vaccine against infection and hospitalization [found in prior studies], and the apparent higher risk of myocarditis following COVID-19 infection than with mRNA vaccination,” lead study author Dr. Naveed Janjua said in the American College of Cardiology news release accompanying the findings.

The authors also said the research should help inform policymakers and individuals choose between Pfizer and Moderna. Those with a propensity for heart conditions may be better off choosing the former, they said.

A number of medical bodies and health professionals have raised concerns about the association between mRNA vaccines and heart conditions. Some have pulled back on recommending the mRNA vaccines for young men in particular due to the less favorable risk-reward balance compared to other demographic groups.