The following is an excerpt from The Vaccine Reaction.
A new study published in the Journal of American College of Cardiology found the risk of myocarditis and pericarditis (heart inflammation) following receipt of an mRNA Covid-19 biological is two to three times higher among individuals who received the Spikevax shot developed by Moderna/NIAID versus the Comirnaty shot developed by Pfizer/BioNTech.
The study was conducted in British Columbia, Canada where the Moderna and Pfizer Covid shots are being widely distributed.
The U.S. Food and Drug Administration (FDA) awarded Moderna and Pfizer an Emergency Use Authorization (EUA) to distribute the mRNA biological products in the United States in December 2020.
According to the Bloomberg Vaccine Tracker, by Oct. 5, 2022 about 613 million doses of Spikevax and Comirnaty had been administered in the U.S.
The main difference between the Moderna and Pfizer mRNA products is that an adult dose of Moderna’s product contains 100 mcg of mRNA, while an adult dose of Pfizer’s product contains 30 mcg of mRNA.
There are also differences in the ingredients contained in both shots, including the type of lipids used to transport mRNA to cells.
Post-marketing evaluations have linked myocarditis and pericarditis (heart inflammation) to mRNA Covid shots.
However, there are very few scientific analyses that have directly compared the safety of the two mRNA Covid shots currently on the market.
The large population-based cohort study analyzed people who received two doses of the mRNA Covid shots and found that post-vaccination myocarditis and pericarditis rates were higher for men and in younger age groups for both biologics, with the highest rate observed in men aged 18 to 39 years following a second dose of Moderna’s Spikevax.
Canadian data showed that the rates of myocarditis after a second dose of the shots were much higher for Spikevax than Comirnaty among individuals 18-39 years of age, with a rate per million doses of 195.5 versus 44.3 among individuals 18 to 24 years old.
The study authors concluded that the “findings may have policy implications regarding the choice of vaccine offered.”
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