https://techcrunch.com/2020/04/16/fda-debuts-new-online-portal-to-encourage-donation-of-plasma-from-recovered-covid-19-patients/

One of the avenues currently being pursued in terms of developing an effective treatment for COVID-19 is through the use of convalescent plasma. Basically, that means using the liquid component of blood from people who have had, and already recovered fully from, COVID-19 to produce treatments that hopefully translate to others the antibodies they developed over the course of fighting off the virus. The FDA has created a dedicated new website seeking recovered COVID-19 donations, and explaining its potential uses.

Use of convalescent plasma is hardly a new concept: It’s been in use since the late 1890s, in fact, and was employed during the 1918 Spanish flu pandemic, albeit with “mixed results.” Modern methods could help improve the efficacy and potential of recovered plasma as a treatment method, and there are a number of drugs in development that use plasma (both animal and human) as the basic active ingredient of their approach.