The FDA Is Investigating Reports of This Rare Moderna Side Effect

Here's why approval of the Moderna vaccine for adolescents is still pending.

Parents across the country celebrated on Oct. 29 when the U.S. Food and Drug Administration (FDA) authorized the use of the Pfizer vaccine in children aged 5 to 11. Kids are now one step closer to being vaccinated against COVID with Pfizer, and adolescents 12 to 15 have been getting Pfizer shots since May. The journey for Moderna, on the other hand, has been less straightforward. While the vaccine manufacturer applied for FDA authorization for children 12 to 17 in June, the agency has yet to approve Moderna in anyone under 18—and the latest update from the company suggests that might not happen until 2022.

RELATED: This One Vaccine Could End the COVID Pandemic, Experts Say.

On Oct. 31, Moderna released a statement saying that the FDA had notified the company it would need more time to assess the use of Moderna's COVID vaccine in adolescents, because of reports of a rare but serious side effect in young people. According to the statement, "On Friday evening, the FDA informed Moderna that the agency requires additional time to evaluate recent international analyses of the risk of myocarditis after vaccination."

Given the need for further analysis, the FDA may not complete its evaluation of the Moderna vaccine in adolescents until Jan. 2022—seven months after the company's initial application.

According to the Centers for Disease Control and Prevention (CDC), myocarditis is inflammation of the heart muscle. Though it is thought to be an extremely rare side effect of vaccination, the CDC notes that cases of myocarditis and pericarditis (inflammation of the heart's outer lining) have been reported most often in young men following the second dose of mRNA COVID vaccines, like Pfizer and Moderna. The CDC adds, "Most patients with myocarditis or pericarditis who received care responded well to medicine and rest and felt better quickly."

The FDA's decision to continue assessing the risk of myocarditis before approving the Moderna vaccine for adolescents comes after several European countries paused the use of the vaccine in young people. As the AP reported, Finland suspended giving Moderna to men under 30 on Oct. 8, because the Finnish Institute for Health and Welfare said that young men and boys were at heightened risk of myocarditis after the shot.

Prior to that, the AP reports, Sweden had stopped giving Moderna to anyone under 30, Denmark had suspended the use in people under 18, and Norway encouraged those under 30 to get the Pfizer vaccine instead. All of these countries made their decision based on an unpublished study from Sweden's Public Health Agency, which suggested "an increased risk of side effects such as inflammation of the heart muscle or the pericardium" in younger Moderna recipients. The study, now being reviewed by European Medicines Agency's adverse reaction committee, said the risk is "very small."

RELATED: For more up-to-date information, sign up for our daily newsletter.

For its part, Moderna maintains that the vaccine is safe and effective in younger recipients. "It is estimated that over 1.5 million adolescents have received the Moderna COVID-19 vaccine. To date, the observed rate of myocarditis reports in those less than 18 years of age in Moderna's global safety database does not suggest an increased risk of myocarditis in this population," the Oct. 31 statement reads.

Paul Offit, MD, director of the Vaccine Education Center at Children's Hospital of Philadelphia and a member of the FDA's vaccine advisory committee, told The New York Times that even with a slightly higher risk of myocarditis in adolescents from Moderna, a COVID infection itself is much more likely to cause myocarditis. Beyond that, cases of myocarditis linked to vaccination tend to be mild and resolve quickly—and are still quite rare.

Nevertheless, the FDA is being extra cautious before approving Moderna for adolescents. The vaccine manufacturer said in its statement, "The safety of vaccine recipients is of paramount importance to Moderna. The Company is fully committed to working closely with the FDA to support their review and is grateful to the FDA for their diligence."

RELATED: This Is What Experts Want You to Know About the Moderna Booster.

Filed Under