The Food and Drug Administration authorized use of convalescent plasma, the antibody-rich blood component taken from recovered COVID-19 patients, for the treatment of serious coronavirus cases.

The agency’s action Sunday, called an emergency-use authorization, permits use of the treatment on hospitalized Covid-19 patients. The Wall Street Journal reported last month the move was coming.

For coronavirus patients and the doctors who treat them, the designation opens up the possibility for faster and easier access to a promising treatment. But the FDA said more clinical studies are necessary for definitive proof of the therapy’s effectiveness.