The agency will narrow its approval for updated coronavirus vaccines, marking a significant shift in the agency’s approach to green-lighting shots that have been recommended broadly to the public.

The agency is changing the standard of evidence required for Covid-19 vaccine approval in the US, Dr. Vinay Prasad, the new director of the FDA’s Center for Biologics Evaluation and Research, and FDA Commissioner Dr. Marty Makary, said in an editorial published Tuesday in the New England Journal of Medicine

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,