Moderna: COVID vaccine has fewer breakthrough cases; slightly higher myocarditis rates

Moderna Chief Medical Officer Dr. Paul Burton defended the company’s COVID-19 vaccine Thursday, saying reports that the drug can cause heart inflammation in some cases is outweighed by the protection it offers against severe disease, hospitalization and death.

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Burton, speaking on a call with reporters, addressed reports about the risk of myocarditis, a rare heart condition, that has been seen in a small number of mostly young men who received the vaccine.

Moderna officials announced last week that the Food and Drug Administration needed more time to make a decision on whether to authorize its vaccine for use in children ages 12 to 17 because of the issue with myocarditis.

Cases of the rare heart inflammation were higher in men under age 30 who received the Moderna vaccine than those who have received the Pfizer-BioNTech COVID-19 vaccine.

Data from studies conducted in France on males ages 12 to 29 showed there were 13.3 cases of myocarditis per 100,000 people for those who had taken Moderna’s vaccine, compared to 2.7 cases per 100,000 people who had gotten the Pfizer vaccine.

German regulators on Wednesday recommended restricting the use of Moderna’s vaccine for those under 30, due to the heart inflammation risk. France, Finland, Sweden, Denmark and Norway have also decided not to allow the vaccine for those under 30.

“While I think health authorities are carefully assessing the data, being appropriately cautious, you can see that they continue to recommend the use of the mRNA-1273 Moderna vaccine,” Burton said on the call. “We believe that the balance of benefit and risk is extremely positive,” he said.

While it is not exactly known why younger men seem to be more likely to suffer myocarditis as a side effect to Moderna’s vaccine, some scientists say hormones, specifically testosterone, may play a role. Burton added that Moderna’s vaccine uses a higher dosage of mRNA in the primary shots than Pfizer’s.

“I do think this hypothesis of testosterone is important,” Burton said. “We know that there is indeed some inflammation associated with testosterone. ... We do have in the primary series, as you know, 100 micrograms of mRNA, so we have slightly higher levels of spike protein, and that could be a contributing factor as well.”

Moderna’s booster shot contains less mRNA –— 50 micrograms –— than the primary shot.

According to CNBC, Burton cited data from the Centers for Disease Control and Prevention on Thursday’s call that showed fewer “breakthrough” COVID-19 cases with the Moderna vaccine than with Pfizer or Johnson & Johnson’s COVID-19 vaccines.

According to the data shared, 86 breakthrough cases per 100,000 received Moderna compared to 135 per 100,000 for the Pfizer vaccine.

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