The FDA's approval was based on a study of 11,400 people age 12 and older that compared the new low-dose vaccine with Moderna's existing vaccine. It found the new vaccine was safe and was at least as effective - and more by some measures - than the original shot, the company said.

Moderna MRNA announced the FDA approval for mRNA-1283, its next-generation refrigerator-stable COVID-19 vaccine, though for a label narrower than initially targeted. The vaccine will be marketed under the brand name mNexspike.