Bloomberg reports:

The Trump administration’s decision to authorize the use of a blood-plasma treatment for Covid-19 with no clear evidence it works could frustrate efforts to better understand the therapy’s benefits.

Several clinical trials are examining the use of so-called convalescent plasma for Covid-19, but none have been completed and results aren’t expected for at least several more weeks.

Some of the studies are struggling to attract participants because of programs that give patients a more certain path to the therapy and a way to avoid the risk of ending up with a placebo in a clinical trial. Researchers fear that Sunday’s decision by the Food and Drug Administration to issue an emergency waiver will make it harder to get patients into clinical trials and get a more definitive picture on whether and how convalescent plasma actually works to treat Covid-19.

Plasma is the liquid portion of the blood. Convalescent plasma collected from those who have recovered from the coronavirus contains antibodies that some researchers say could help patients who have been newly diagnosed with Covid-19. President Donald Trump has called the therapy “something very special.”

The emergency-use clearance followed accusations by Trump that U.S. regulators had held off in order to dim his chances of re-election. Some senior U.S. health officials had been reported to have cautioned against issuing a clearance until researchers could collect more data.

Antibodies are one of the main infection-fighting compounds produced by the immune system. They remain in the blood of patients who have recovered from disease, and using them to help another person fight infection is an old idea. Convalescent serum was used to fight the 1918 flu pandemic. The first Nobel Prize in Physiology or Medicine was awarded to Emil von Behring in 1901 for his work studying serum therapy for diphtheria.

However, there are many questions that remain about what convalescent plasma is and who should get it. People sickened by a pathogen produce their own antibodies; sorting out which antibodies actually fought off a disease is a complicated task for researchers. Doctors also want to make sure that introducing foreign antibodies won’t make people sicker. [Continue reading…]