After studying preliminary data from 35,000 coronavirus patients treated with plasma therapy, Mayo Clinic researchers have confirmed that there were fewer deaths among people given plasma within three days of diagnosis, and also among those given plasma containing the highest levels of virus-fighting antibodies.
However, the researchers have also warned that since it wasn’t a formal study, any conclusion about the efficacy of the treatment cannot be drawn yet.
The patients were treated in different ways in hospitals around the country as part of a Food and Drug Administration program designed to speed access to the experimental therapy. That so-called “expanded access” program tracks what happens to the recipients, but it cannot prove the plasma—and not other care they received—was the real reason for improvement.
However, Mayo lead researcher Dr. Michael Joyner calls it “signals of efficacy”, which can be explored further.
Convalescent plasma is not a new approach. It has been a century old approach to fend off flu and measles before vaccines. It’s a go-to tactic when new diseases come along, and history suggests it works against some, but not all, infections.
Plasma is the liquid portion of blood that remains when all red and white blood cells and platelets have been removed. It was over a hundred years ago that Emil Behring was awarded the first Nobel prize for physiology and medicine for his work demonstrating that plasma could be used to treat diphtheria.
“For 102 years we’ve been debating whether or not convalescent plasma works,” said Dr. Mila Ortigoza of New York University, referring to plasma’s use in the 1918 flu pandemic. This time around, “we really need undisputable evidence.”
The Mayo findings were posted online ahead of scientific peer review. They show that 20% of people given high-antibody plasma within three days of diagnosis had died within 30 days compared with 30% of people treated later with low-antibody plasma.
A spokesperson of the USFDA was quoted as saying the agency could not comment on the investigators’ data analysis and conclusions as it was assessing all available evidence that could potentially support the use of convalescent plasma.
However, the FDA has been closely considering if the evidence is good enough to allow so-called emergency use of convalescent plasma, a step that would make it even harder for more rigorous testing to be completed.
According to the American Association of Blood Banks (AABB), many Covid-19 survivors have donated their plasma. Still, Blood banks want more, and have requested the survivors to donate.
Scientists want to know all aspects of plasma:
- Does it generally help?
- When is the right time to use it?
- Should it be used with the very sick, or the earliest sign of infection is the right time to start this treatment.
- What is the right does of plasma?