What is convalescent plasma therapy for COVID-19?

Convalescent plasma for COVID-19 is collected from eligible patients who have fully recovered from the virus. This plasma can be harvested and used for patients with weak immune systems who lack options for COVID-19 treatment. It can be useful for illnesses with no vaccine or treatment, but it is not commonly used for COVID-19 treatment today.

What is convalescent plasma?

Convalescent plasma is a liquid part of the blood that contains antibodies (proteins) to certain infections, such as to COVID-19. Antibodies are proteins that your immune system makes in response to an infection. They can kill the virus and help you recover.

Convalescent plasma for COVID-19 is collected from eligible patients who have fully recovered from the virus. This plasma can be harvested and used for patients who lack options for COVID-19 treatment.

Patients who donate this type of plasma must have a documented laboratory-confirmed diagnosis of COVID-19, negative results of the disease, and complete resolution of symptoms for at least 14 days prior to donation.

Convalescent plasma therapy is a century-old technique used to supply antibodies to critically ill patients who have few, if any, treatment options left. Convalescent plasma therapy has been used in many other viral illnesses in past history, including Ebola, diphtheria, 2003 SARS-CoV, the 2009 influenza A (H1N1) outbreak, and even the Spanish flu pandemic of 1918.

During convalescent plasma therapy, plasma from blood donors who have recovered from COVID-19 is infused into patients to supply a source of antibody against the coronavirus (SARS-CoV-2). Convalescent plasma may be a treatment option for some patients with COVID-19 with weak immune systems, but it is not commonly used today.

People who received COVID-19 convalescent plasma therapy today usually receive it along with an antiviral treatment.

How does convalescent plasma therapy work?

Convalescent plasma therapy works differently than a vaccine.

When you receive a vaccine, your immune system produces its own antibodies to the microbe you are being protected against. These antibodies have a type of memory, and when you are exposed to the target virus or bacteria in the future, your body is able to activate the antigens and attack the pathogen. Some vaccines can last a lifetime with one shot. This is known as “active immunity”.

Convalescent plasma therapy offers a short-term type of “passive immunity”. You receive the antibodies via injection of plasma from a donor who has successfully fought off the COVID-19 disease. The antibodies may help fight off the virus and allow a patient time to develop their antibodies for recovery.

How is convalescent plasma collected?

Convalescent plasma is collected from you by a sterile process known as plasmapheresis, when plasma is separated from whole blood. A single needle is placed in a vein in your arm. Your blood is collected into a machine and the plasma is isolated into a special bag. Your red blood cells are returned to you through the same needle. The entire process takes about 40 to 60 minutes and is similar to donating blood.

Is convalescent plasma therapy effective for COVID-19?

A 2020 open-label study of COVID-19 plasma therapy enrolled over 35,000 patients, but did not contain a control (placebo) group, so the true treatment effect could not be determined.

The main outcome measures was 7- and 30-day mortality. Patients were critically ill, with 52.3% in the intensive care unit (ICU) and 27.5% receiving mechanical ventilation at the time of plasma transfusion.

The seven-day mortality rate was 8.7% [95% CI 8.3%-9.2%] in patients transfused with plasma within 3 days of COVID-19 diagnosis but 11.9% [11.4%-12.2%] in patients transfused 4 or more days after diagnosis (p<0.001).

Similar findings were observed in 30-day mortality (21.6% vs. 26.7%, p<0.0001). Higher concentration of antibodies in the transfused plasma appeared to be linked with lower mortality rates.

Researchers are still studying the effect of COVID-19 plasma therapy.

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Are there side effects with convalescent plasma therapy?

Plasma transfusions are generally safe and well-tolerated by most patients, and donated blood is tested for safety, but serious side effects have been reported.

Possible side effects include:

• mild fever
• allergic reactions
• transfusion reactions
• bronchospasm
• acute lung injury
• very rare risk of infectious disease transmission via the donated plasma (i.e., HIV, hepatitis B or hepatitis C virus)

Donors of COVID-19 plasma therapy are tested before they donate, so there is no real risk of contracting COVID-19 from the plasma.

In June 2020, Mayo Clinic released results from a large study with 20,000 patients that suggested COVID-19 plasma therapy was safe in a diverse group of patients. Serious adverse event rates were low and less than 1%, including transfusion reactions and thrombotic (blood clotting) events. Adverse cardiac events occurred in about 3% of patients, but 88% of these events were deemed unrelated to the plasma transfusion by the treating physicians.

I have recovered from COVID-19. Can I donate convalescent plasma?

If you have recovered from COVID-19 and you are eligible to give blood donations, you may be able to donate. Certain conditions must be met:

1. You must have had a prior diagnosis of COVID-19 documented by a laboratory test and meet other laboratory criteria. If you did not receive a test for COVID-19, and only think you might have had it, you are not eligible to donate.
2. You must have fully recovered from COVID-19 without any symptoms for at least 14 days before donation, and have a repeat test that shows that you are now negative for COVID-19

Contact your local blood banks or ask your doctor about convalescent plasma donations for COVID-19. Collection of plasma for COVD-19 is not as common as it was at the beginning of the pandemic. Many blood banks may not be collecting convalescent plasma at this time.

Bottom Line

Convalescent plasma for COVID-19 is collected from eligible patients who have fully recovered (without symptoms) from the virus for at least 14 days. Donors who are eligible may donate through the American Red Cross or other local blood banks, but call first to see if they are actively collecting. Many blood banks may not be collecting convalescent plasma at this time.

In order to donate you will need to meet other specific criteria, including a documented lab test that proves you had a diagnosis of COVID-19, and are now fully recovered from the virus.

The FDA has approved an Emergency Use Authorization (EUA) process for convalescent plasma therapy for patients. An EUA can be issued on an investigational agent when the FDA believes a treatment is effective in treating COVID-19 and that the potential benefits of the product outweigh the potential risks. The EUA maintains that high levels of anti-SARS-CoV-2 antibodies (i.e., high-titer products) must be used.

Based on NIH guidelines, the use of COVID-19 convalescent plasma for the treatment of COVID-19 in hospitalized patients who are immunocompetent is not recommended.

Today, with the availability of antivirals like Paxlovid and preventive vaccination for COVID-19, convalescent plasma use has declined.

More resources

• COVID-19: Prevention, Treatment and Vaccines

This is not all the information you need to know about COVID-19 treatment for safe and effective use and does not take the place of your doctor’s directions. Review the full product information and discuss this information and any questions you have with your doctor or other health care provider.