What Is Convalescent Plasma?
Apr 15, 2020 Katie Rosenblum
As doctors and researchers around the world learn more about COVID-19 (coronavirus), potential treatment options are beginning to emerge. One of these treatment options being explored uses convalescent plasma, or plasma from recovered patients.
To learn more about the potential of this therapy, we sat down with Dr. Ellen Klapper, medical director of Transfusion Medicine at Cedars-Sinai.
What is convalescent plasma?
Dr. Ellen Klapper: This is plasma that is collected from people who have recovered from a disease, whose blood is presumed to have antibodies for that disease. These antibodies are what helped the person fight off the initial infection.
The thought is that these antibodies, present in the plasma of people previously infected and now recovered, might help treat patients who are not able to fight the infection themselves.
The optimal treatment for COVID-19 is still being investigated, and many things are being looked at. This is one potential therapy.
What do we know about convalescent plasma?
Dr. Klapper: Convalescent plasma isn't new. This has been used and studied historically in many instances. It was used in the past to fight polio, hepatitis, influenza and many other viruses.
It's important to note this is not the same as a vaccine. Convalescent plasma results in a passive transfer of antibodies, whereas a vaccine stimulates a person's immune system to create antibodies for themselves.
Has convalescent plasma been used successfully in COVID-19 patients?
Dr. Klapper: Convalescent plasma for COVID-19 is still in its infancy, but there have been limited, preliminary reports of success in a few patients in China and in small numbers of patients elsewhere.
There are anecdotal reports in the U.S., but it deserves careful study so we can fully understand its benefits.
Who qualifies to donate convalescent plasma?
Dr. Klapper: People who are eligible must first meet all regular blood donor criteria. They also have to have had a documented case of COVID-19, either by a positive test for the virus during the illness or a positive test for antibodies after they recovered. Lastly, they have to be healthy for 28 days since their last symptoms.
Testing has been limited in many areas, so there are people who suspect they had it but weren't tested. Unfortunately, without a test they don't qualify to donate at this time.
How is convalescent plasma being used for COVID-19 patients?
Dr. Klapper: This is considered an investigational product at this point, so there are strict FDA (Food and Drug Administration) rules for how this can be used. There are three ways hospitals and doctors can use convalescent plasma for COVID-19 patients. They are:
Clinical trials: Patients can be enrolled in a clinical trial, which is a controlled study to determine the safety and efficacy of this product.
Many people in this country don't have access to clinical trials for a variety of reasons, so the FDA has created two other ways for people to have access.
Emergency investigational new drug application (eIND): An eIND allows a treating doctor to apply for one dose of the plasma for a single patient. The application is generally turned around within hours.
Expanded access: Rather than applying and administering to one patient at a time, a hospital can register through a central study at the Mayo Clinic and obtain plasma that way.
There are also criteria for patients receiving convalescent plasma. They have to be ill enough to be hospitalized, and they have to show signs of respiratory distress—among other things. At this point, it is not intended for patients who are recovering at home.
For those who qualify, what happens when they come to donate?
Dr. Klapper: Plasma is the liquid part of blood and can be collected by apheresis, so in that way it's similar to the process used for platelet donation. A machine separates the plasma from the red blood cells and platelets, and those cells are returned to the donor. We collect the plasma by itself into a bag, and then it is stored in a freezer in the blood bank for future use.