“We are definitely aware of patients who have refused blood products from vaccinated donors,” said Dr. Julie Katz Karp, who directs the blood bank and transfusion medicine program at Thomas Jefferson University Hospitals in Philadelphia.

Emily Osment, an American Red Cross spokesperson, said her organization has fielded questions from clients worried that vaccinated blood would be “tainted,” capable of transmitting components from the covid vaccines. Red Cross officials said they’ve had to reassure clients that a covid vaccine, which is injected into muscle or the layer of skin below, doesn’t circulate in the blood.

“While the antibodies that are produced by the stimulated immune system in response to vaccination are found throughout the bloodstream, the actual vaccine components are not,” Jessa Merrill, the Red Cross director of biomedical communications, said in an email.