The availability of coronavirus vaccines for younger children could be delayed, after the Food and Drug Administration asked Pfizer and Moderna to expand its trials. The agency wants to know if a rare inflammation of the heart muscle that has surfaced in young adults would more of a problem in young children, the Washington Post reports. The number of children to be enrolled in the trials was not announced. Moderna said it already had planned to involve about 7,000 children down to 6 months old, per the AP. A Moderna spokesman said authorization for administering the company's vaccine could be given this winter or early in 2022. "The objective is to enroll a larger safety database, which increases the likelihood of detecting rarer events," he said.
Pfizer had planned to test its vaccine in 4,500 children, ages 6 months to 12 years, and report its findings by November. The Centers for Disease Control and Prevention has determined a "likely" connection between vaccine doses and myocarditis, which has shown up more often in adolescents who've been vaccinated than adults. Teenagers and adults receive identical dosages, but smaller ones might be necessary for children. The FDA has not decided how large it wants the trials to be for children younger than 5. Pfizer's vaccine is approved for recipients as young as 12; Moderna is expecting similar approval from the FDA any time now. (Dr. Anthony Fauci supports developing prototype vaccines.)