Convalescent plasma (kon-vuh-LES-unt PLAZ-muh) therapy uses blood from people who've recovered from an illness to help others get better.

When the body clears out a virus, a person's blood has immune system proteins called antibodies. To get convalescent plasma, people donate blood after recovery. The blood is processed to remove blood cells, leaving behind a liquid called plasma.

The plasma has different amounts of antibodies used to block the virus that caused the illness. Plasma with a high level of antibodies may help people with the same illness recover.

Convalescent plasma therapy isn't a new idea. It has been used as a treatment for pandemic influenza, Lassa virus, Ebola virus and others.

In 2020, doctors used convalescent plasma therapy to treat coronavirus disease 2019 (COVID-19). The U.S. Food and Drug Administration gave emergency authorization for COVID-19 convalescent plasma to be used, and it is still an option for people who have weakened immune systems.

Convalescent plasma therapy is used to prevent or treat severe or life-threatening complications from an illness. In theory, it helps by providing antibodies the immune system can't make or can't make fast enough.

This therapy may be used if an illness has no vaccine or treatment. It also may be used if a person's immune system can't respond fast enough to a viral infection.

In 2020 no treatments existed for COVID-19. At that time, COVID-19 convalescent plasma may have helped some people who were in the hospital with COVID-19 recover faster. By 2022 the virus that causes COVID-19 had mutated. Some medicines used to treat or prevent serious illness no longer worked. So COVID-19 convalescent plasma was authorized for use by people who were not in the hospital for COVID-19 and who had weakened immune systems to lower the risk of serious COVID-19 illness.

COVID-19 convalescent plasma with a high level of antibodies may be used to help people diagnosed with COVID-19 who have a weakened immune system. This type of plasma is often donated by people who were vaccinated for COVID-19 and then caught the virus that causes COVID-19 afterward.

Researchers continue to look into when and if this treatment helps.

Convalescent plasma therapy has the same risks as any plasma therapy. These risks include:

• Allergic reactions.
• Lung damage and difficulty breathing.
• Infections such as HIV and hepatitis B and C.

The risk of these infections is low. Donated blood is tested for safety. And people may have mild complications or none at all. Other people may have severe or life-threatening complications. In the case of COVID-19 convalescent plasma, donors are tested before they give blood. So there is no real risk of getting COVID-19 from the donated plasma.

Your doctor may consider convalescent plasma therapy in limited situations.

If you have COVID-19 and your immune system is weakened by treatment or disease, convalescent plasma therapy may be an option. If you have questions about convalescent plasma therapy, ask your doctor.

Your doctor will order convalescent plasma that is compatible with your blood type from your hospital's local blood supplier.

Before the procedure

To get ready, your care team will use a needle to enter a vein in one of the arms. This sterile single-use needle is connected to a port. Fluids or other medicines can be added to the vein when tubing called an intravenous, or IV, line is connected to the port. Often this tubing is connected to a bag that hangs next to you.

During the procedure

When the plasma arrives, the sterile plasma bag is attached to the tube. You will be closely observed for the first 15 minutes since that is when transfusion reactions occur. The plasma drips out of the bag and into the tube. Completing the transfusion takes 1 to 2 hours.

After the procedure

Once the COVID-19 convalescent plasma is done being transfused, you can go home if you aren't a patient in the hospital. A member of your care team will assess your response to the treatment. You may get another bag, also called a unit, of COVID-19 convalescent plasma. Most commonly you will be treated with an anti-viral medication in addition to COVID-19 convalescent plasma.

In the past, records of convalescent plasma treatment show it has helped to prevent and treat disease when no other option existed. But research on convalescent plasma treatment continues.

Data from clinical trials, studies and a national access program suggested that COVID-19 convalescent plasma with high antibody levels may lessen the severity or shorten the duration of COVID-19 in some people with weakened immune systems.

But scientists continue to research the safety and how well convalescent plasma therapy works in a range of diseases and people.