Blood plasma — the yellowish, cell-free portion that remains after red and white blood cells and have been filtered out by a machine and returned to the plasma donor — is rich with antibodies. Plasma from recovered COVID-19 patients might prove useful in preventing infection as well as in treatment, scientists say.

A phlebotomist shows Melissa Cruz the full bag of her donated convalescent plasma, which she donated after recovering from coronavirus (COVID-19) contracted during her work as an ER technician, at the Central Seattle Donor Center of Bloodworks Northwest during the outbreak in Seattle, Washington, U.S. April 17, 2020. The plasma from recovered patients will be used in an experimental treatment study for current coronavirus patients. REUTERS/Lindsey Wasson – RC2N6G962ZX1