Federal regulators from the Food and Drug Administration have requested that Pfizer and Moderna increase the number of children in their testing trials, signaling a potential delay in the availability of Covid-19 vaccines for children under the age of 12, according to the Washington Post.
Some experts and government officials have signaled that a coronavirus vaccine for children might become available by early fall, but the timeline remains unclear.
The federal agency made the request to determine if myocarditis, or inflammation of the heart, might be more common among younger children who receive the vaccine. The condition is more likely to develop in adolescents who have received a coronavirus vaccine, though it remains rare and the risk is low.
Moderna’s original trials included 7,000 children, and Pfizer’s original trial size was 4,500 children. Both trials included children ages 6 months to 12 years. It is unclear how many more children will be joining the trials.