Coronavirus: What is convalescent plasma therapy?

A newly approved treatment with some history of success could offer hope for the sickest of the country’s COVID-19 patients.

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The U.S. Food and Drug Administration has approved the use of convalescent plasma therapy as an experimental treatment in clinical trials and for critically ill COVID-19 patients without other treatment options.

The therapy, which takes antibodies from the blood of a person who has recovered from a virus and transfuses those antibodies into a person sick with that virus, has long been used as a way to help kickstart a person’s immune system.

Since the March 24 FDA approval, 11 critically ill COVID-19 patients in New York City and Houston received experimental treatment using convalescent care. The results of those cases have not been reported yet.

The therapy has also been used in other parts of the world.

A study of 10 patients in China who have undergone convalescent therapy showed a shortening of the duration of symptoms, improve oxygen levels and a drop in the “virus load” or the amount of virus in a person’s body.

With a vaccine likely months to a year away, scientists hope that convalescent plasma therapy can help those sickest with the virus now.

How does the therapy work, who can it help and what are the results so far? Here’s what we know about convalescent plasma therapy.

What is convalescent plasma?

Convalescent plasma therapy involves transfusing certain components from the blood of people who have had the COVID-19 virus and recovered into people who are very sick with the virus or people who are at high risk of getting the virus.

How does it work

As people fight the COVID-19 virus, they produce antibodies that attack the virus. Those antibodies, proteins that are secreted by immune cells known as B lymphocytes, are found in plasma, or the liquid part of blood that helps the blood to clot when needed and supports immunity.

Once a person has had the virus and recovered, that person has developed antibodies that will stay in their blood waiting to fight the same virus should it return. Those antibodies, when injected into another person with the disease, recognize the virus as something to attack.

In the case of the coronavirus, scientists say antibodies attack the spikes on the outside of the virus, blocking the virus from penetrating human cells.

Who would it help?

Researchers hope that convalescent plasma will be effective in treating people with the most severe symptoms of the virus. Additionally, it is hoped that it can keep those people who are not as sick from COVID-19 from getting any sicker.

Convalescent plasma is also known as passive antibody therapy, meaning that while it can immediately provide a person with antibodies to fight a virus, those antibodies only last a short period of time in the recipient’s body.

Doctors hope the antibodies can fight back the virus until a person develops their own defenses.

How many patients can be treated with plasma from a donor?

One person’s donation of plasma can produce two doses of the material needed for transfusions. Scientists say that a person only needs one transfusion to get enough antibodies to fight a virus.

Who is conducting trials on convalescent plasma therapy?

Thirty-four institutions around the country are part of the National Covid-19 Convalescent Plasma Project. The project is asking people who have had the virus and are at least 21 days out from the onset of the first symptoms to donate plasma. The project was self-organized by medical researchers across the country.

Mount Sinai Hospital in New York City has partnered with the FDA on clinical trials on convalescent plasma and is treating three patients with the therapy. Johns Hopkins Bloomberg School of Medicine in Baltimore, Maryland, is also conducting convalescent plasma trials.

A study from China suggested that the use of convalescent plasma treatment was successful in treating five critically ill patients.

Is it a new treatment?

The idea of using one person’s antibodies to help another person fight a virus is not new. Reports show that as far back as the 1890s, some form of the therapy was being tried. Convalescent therapy was used to treat measles and mumps.

The downside of the treatment is that it is expensive and limited by the number of donors since one donation can make only two doses of the therapy.

Who can donate?

Different trials may have different requirements for participation. The American Red Cross is asking people to donate plasma for trials as long as participants meet these guidelines:

  • Are at least 17 years old and weigh at least 110 lbs.
  • Are in good health and feeling well.
  • Have a prior diagnosis of COVID-19 and meet specific laboratory criteria.
  • Must be symptom-free for at least 14 days prior to donation.

If you meet all the criteria above and are willing to help, the Red Cross is asking you to complete the Donor Request form.

Is it working?

According to the FDA, “It is not currently known if convalescent plasma will be an effective treatment against COVID-19,” but news of success from studies around the world are showing promise.

A study published in the Journal of the American Medical Association described encouraging results when it was used in five critically ill patients who had both COVID-19 and acute respiratory distress syndrome (ARDS). All five patients in the study recovered.

The study noted that more research is needed as the study included only five patients.

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