Moderna Inc. said it would expand an ongoing trial of its coronavirus vaccine in children under 12 years old to gather more safety data amid worries that messenger RNA shots may trigger rare heart side effects.
“The objective is to enroll a larger safety database which increases the likelihood of detecting rarer events,” a Moderna spokeswoman said in a statement.
Clinical trial timelines are regularly re-evaluated based on regulatory agency discussions and requests, she said, and Moderna expects to have data that would support authorization in late 2021 or early 2022. The Cambridge, Massachusetts-based company is discussing a proposal for a bigger trial with the U.S. Food and Drug Administration, she said.
Concerns about side effects from both the Moderna and Pfizer Inc.-BioNTech SE mRNA-based vaccines have risen after reports of rare cases of heart and heart-lining inflammation in young adults.
Moderna shares declined 3.9% to $335.35 at 3:45 p.m. Monday in New York. Shares of Pfizer were up 0.4%, while BioNTech’s American depositary receipts rose 1.4%.
Federico Laham, medical director for children’s infectious diseases at Orlando Health Arnold Palmer Hospital for Children in Florida, said expanding the size of the trials for the under-12 age group will help families weigh the benefits and risks of vaccination.
“I welcome this cautious approach,” he said in an interview. “The more you vaccinate, the more you’re likely to see rare side effects. Though including more patients may delay approval for that age group, it will instill a sense of security and safety for the intended population.”
The New York Times reported earlier Monday that both Moderna and the Pfizer-BioNTech partnership were expanding the size of their pediatric COVID-19 vaccine trials at the request of the FDA. Pfizer declined to comment on whether its trial had gotten bigger.
FDA spokesperson Abby Capobianco said the agency generally works with companies to ensure that clinical trials are of adequate size to detect safety signals, but declined to comment on the vaccine trials specifically.
Moderna’s late-stage children’s trial began in March and was originally planned to enroll 6,750 kids from ages 6 months old through 11 years old. A listing on clinicaltrials.gov currently projects 6,975 participants. The company said that it couldn’t confirm the scope of the expansion.