The FDA plans to require new clinical trials for approval of annual COVID-19 boosters for healthy Americans under 65.

The U.S. Food and Drug Administration plans to require new clinical trials for approval of annual COVID-19 boosters for healthy Americans under 65, effectively limiting their availability this fall to older adults and those with a higher risk of developing severe illness,

While details of the guidance remain closely held, some clues are likely found in the FDA’s late Friday letter approving Novavax’s Covid vaccine. Who can get it: The license covers a limited population — adults 65 and older and people ages 12 to 64 with at least one underlying condition putting them at high risk for severe disease — compared with the two messenger RNA shots available for Covid recommended for all people 12 and older.