https://techcrunch.com/2020/03/24/fda-now-allows-treatment-of-life-threatening-covid-19-cases-using-blood-from-patients-who-have-recovered/

The U.S. Food and Drug Administration (FDA) has updated its rules around use of experimental treatments for the ongoing COVID-19 pandemic to include use of ‘convalescent plasma,’ in cases where the patient’s life is seriously or immediately threatened. This isn’t an approval of the procedure as a certified treatment, but rather an emergency clearance that applies only on a case-by-case basis, and only in extreme cases, as a means of helping further research being done into the possible efficacy of plasma collected from patients who have already contracted, and subsequently recovered from, a case of COVID-19.

Plasma is a component of human blood – specifically the liquid part – which contains, among other things, antibodies that contribute to a body’s immune response. Use of plasma, through direct transfusion into a patient, like every other proposed treatment for COVID-19 (and the SARS-CoV-2 virus that causes it), has not undergone the clinical studies needed to show that it’s actually safe and effective in combatting the disease.