Risk of Myocarditis Drags Moderna on Offering COVID Vaccines to Population Under 18
Molly Huang ‘23
Use of Moderna's COVID-19 vaccines on adolescents in the U.S. will be delayed to evaluate the increased risk of myocarditis after vaccination. The U.S. Food and Drug Administration (FDA) notified Moderna on October 29 that it needs more time to review Moderna's Emergency Use Authorization (EUA) request on administering its “COVID-19 vaccine (mRNA-1273) at the 100 µg dose level in adolescents 12 to 17 years of age.” The review may not be completed until January 2022. The CDC extended the assessment based on current evidence that certain groups like young men had a higher risk of developing myocarditis after receiving Moderna COVID-19 vaccines (around 11 cases for every 100,000 male recipients between 16 and 29 in one study). Myocarditis is an inflammation of the heart muscle that causes symptoms including rapid or irregular heartbeat. The gender difference in the risk level of myocarditis is still unknown.
A few other countries also restricted the use of the Moderna vaccine on young people for this reason. After an unpublished study by Sweden's Public Health Agency showed an increased risk of heart muscle or pericardium inflammation, Finland, Sweden, Denmark, and Norway curbed the use of Moderna on young people in October.
In contrast, the Pfizer-BioNTech (Pfizer) vaccine seems less likely to cause this side effect and continues to be available for youths in these areas. The product comparison study done by the Kaiser Permanente Vaccine Study Center demonstrates that the incidence rate of myocarditis rose after a dose of either Pfizer or Moderna vaccine among people between 18 and 39 years old. However, the rate after Moderna was consistently higher in different gender groups. Moreover, for the same age group, the risk of myocarditis in the 18-39 age group receiving two Moderna shots was almost twice the risk of their counterparts receiving two Pfizer shots. Due to lower risk, the Pfizer vaccine is still approved for adolescents in Norway and the U.S, while Moderna’s is curbed.
Though rare but possible side-effects of myocarditis exist in both Moderna and Pfizer vaccines, they are relatively minor compared with the harm of infecting the COVID-19 virus. Experts familiar with recent studies said that the absolute risk of developing myocarditis is still negligible. In most cases, the side effects are milder and more short-lived than the damage from the COVID virus. Thus, even knowing mRNA vaccines have this potential side effect, the FDA still allowed the Pfizer vaccine to be used on children between 5 and 11 years old during the last week.
In the short term, the Pfizer-BioNTech, instead of Moderna, will be the dominant mRNA COVID vaccine for adolescents. Due to the restraint on administering its vaccine to adolescents in some countries, Moderna will delay filing a request for EUA of mRNA-1273 at the 50 µg dose level in children between 6 and 11 years old. The higher risk of myocarditis makes Moderna lag behind when competing with Pfizer in the adolescent COVID vaccine market. Since the adolescent market is considerably large, with around $680 million merely for the age group of 12-15 in the U.S., the delay of CDC approval will incur huge costs for Moderna. More importantly, the supply of COVID vaccines will be constrained due to this safety reason, which will impact many adolescents in countries with an insufficient vaccine supply. At present, we still need additional evidence and analyses on different mRNA COVID vaccines' side effects and effectiveness, which would help the world promote COVID vaccination and combat the pandemic.
Sources:
https://www.fool.com/investing/2021/05/25/how-the-adolescent-covid-vaccine-market-could-be-h/
https://www.cbsnews.com/news/moderna-covid-19-vaccine-fda-delays-decision-myocarditis/
https://www.cdc.gov/vaccines/acip/meetings/downloads/slides-2021-10-20-21/08-COVID-Klein-508.pdf
https://www.nytimes.com/2021/11/01/health/covid-kids-children.html
https://www.mayoclinic.org/diseases-conditions/myocarditis/symptoms-causes/syc-20352539
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