It’s been nearly two years since Moderna’s COVID-19 vaccine made its debut in the U.S., but research on the shot is far from over. Now, a new study has flagged higher risks of heart inflammation associated with Moderna's shot compared with the rival from Pfizer and BioNTech.
Published in the Journal of the American College of Cardiology, the study concluded that the risk of myocarditis is two to three times higher after a second dose of Moderna's Spikevax compared with Pfizer and BioNTech’s Comirnaty.
Cases of myocarditis, or inflammation of the heart muscle, were most prevalent in men under 40 years of age who received the Moderna vaccine, the study found. Researchers noted that the findings support the idea of recommending specific vaccines to certain populations to minimize adverse events.
Moderna acknowledged the “known and rare risk” of the side effect, noting in an emailed statement to Fierce Pharma that cases are “generally mild” and resolve after a few days of “treatment and rest.” At a population level, the "risk of myocarditis after COVID-19 infection is much higher than after COVID-19 vaccination,” a company spokesperson said.
"Regulatory agencies around the world have stated that the benefits of COVID-19 mRNA vaccines significantly outweigh the risk across all age groups," the spokesperson added. "Vaccination against COVID-19 continues to be a critical tool in overcoming the impacts of the global pandemic.”
The study looked at data from about three million participants who had received two primary doses of either Pfizer or Moderna’s vaccine in British Columbia, Canada, between January 2021 and September 2021.
In all, the team identified 31 myocarditis cases within 21 days of the second Moderna dose, compared with 21 after the second Pfizer shot. After accounting for the number of people who received each shot, they calculated a rate of 35.6 cases per million for Moderna's vaccine and 12.6 per million for Pfizer's shot.
The highest rates for Moderna’s vaccine fell in the range of males aged 18 to 29 years of age.
The company stressed that patient safety is its top priority.
For its part, the CDC stresses that myocarditis is a rare side effect overall, but that it's “actively monitoring” reports of both myocarditis and pericarditis, which is inflammation of the outer lining of the heart.
The vaccine garnered $3.4 billion for Moderna during the third quarter. The company lowered its full-year sales guidance to between $18 billion and $19 billion from its previous forecast of $21 billion.