The Food and Drug Administration (FDA) has asked Pfizer and Moderna to expand their COVID-19 vaccine trials for 5 to 11-year-olds in an effort to determine whether a rare side effect in the form of heart inflammation is more common among younger groups, according to reports.
A spokesman for Moderna confirmed to The Washington Post that the company is “actively discussing a proposal” with the FDA to expand its trial “to enroll a larger safety database which increases the likelihood of detecting rarer events.” The spokesperson added that a final number for the size of the trial has yet to be determined.
The New York Times report said Pfizer is also in talks to expand its vaccine trials in younger children, with a spokesperson for the company telling CNN that it has no updates to its previous trial timelines or details.
Pfizer earlier said that it planned to enroll around 4,500 children between 6 months and 11 years old in the United States, Finland, Poland, and Spain at over 90 clinical trial sites, although the size of the 5-to-11-year-old cohort is unclear.
The expanded trials are meant to help regulators better understand the potential side effects associated with Moderna’s and Pfizer’s mRNA vaccines in younger populations.
In a report on adverse vaccine events, the Centers for Disease Control and Prevention (CDC) said that as of July 19, health officials have confirmed 674 reports of myocarditis or pericarditis among people aged 30 and younger who received COVID-19 vaccines. Myocarditis is inflammation of the heart muscle, while pericarditis is inflammation of the lining that surrounds the heart. Most of the cases were reported after people received Pfizer’s and Moderna’s vaccines, the CDC noted, adding that the agency “and its partners are investigating these reports to assess whether there is a relationship to COVID-19 vaccination.”
In June, the FDA added a warning about the risk of developing myocarditis or pericarditis to its patient and provider fact sheets for Moderna’s and Pfizer’s mRNA-based vaccines. Both the Moderna fact sheet (pdf) and Pfizer’s (pdf) say that reports of adverse events suggest increased risk of myocarditis and pericarditis within a few days after receiving the vaccine, and “particularly following the second dose.”
The CDC says cases of myocarditis and pericarditis after COVID-19 vaccination are rare, insisting the vaccines are safe and effective and recommending “everyone 12 years and older get vaccinated as soon as possible.”
But according to numerous studies, the risk of death or severe illness from COVID-19 in children is extremely low.