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COVID-19: Plasma and Antibodies

What is Convalescent Plasma?

Convalescent plasma is plasma that is taken from a person who has recovered from a virus. When a person is first infected with a virus, their immune system generates antibodies to combat the virus. By transferring these antibodies to other people infected with the virus, it can act as a treatment to help them fight it off.

In order to get this plasma, plasma donors through a registered blood donation service are required. Canadian Blood Services requests that all donors follow pre-existing donor requirements:

  • Between 16-67 years old

  • Previously confirmed positive for COVID-19 through a lab test

  • Fully recovered from the virus and asymptomatic for a minimum of 28 days

This is a part of a national clinical trial to test the safety and effectiveness of convalescent plasma in the treatment of COVID-19.

Convalescent Plasma Therapy

The antibodies in question are proteins produced by the immune system to fight off infections. The treatment mentioned above is called convalescent plasma therapy (CPT) because these antibodies are found in plasma—the clear, liquid portion of the blood.

Who Can Benefit?

Individuals with COVID-19 are at risk of becoming severely ill if they do not respond to treatment, and can further develop a severe lung condition called acute respiratory distress syndrome (ARDS). This lung condition forces patients to adopt mechanical assistance (ventilators) in order to breathe, increasing their risk of multisystem organ failure.

The idea behind this therapy is that it can help people who are currently fighting COVID-19 and are not benefiting from other treatment options.

It can also help those who have comorbidities that would increase the fatality of COVID-19, were they to be infected. Comorbidities can include heart disease, chronic obstructive pulmonary disease (COPD), diabetes, cancer, hyper/hypotension, and hyper/hypoglycemia. When these individuals receive convalescent plasma therapy, they can be prevented from getting sicker.

Convalescence plasma therapy can also be considered for those who have been exposed to someone with COVID-19, including family members of sick patients or healthcare workers. CPT can prevent them from potentially contracting the virus in the future.

What are the Risks?

Given the history of blood and plasma treatments, they are usually safe. There is a low risk of contracting COVID-19 from receiving convalescent plasma therapy. Researchers believe that the low risk is credited to the fact that the plasma donor has fully recovered from the disease.

However, convalescent plasma therapy carries the risk of allergic reactions, lung damage, breathing difficulties, and transmission of secondary infections such as HIV, hepatitis A, or hepatitis B. The risk of these infections due to CPT are very low, as donated blood must meet stringent requirements.

History of CPT

Convalescent blood products (CBP) are not new treatments; they have existed since the late 1800s. Back then, these products were used to treat diphtheria, scarlet fever, and pertussis. 

Versions of convalescent blood products were also widely used in the Spanish Influenza epidemic that lasted from 1918-1920. 

During the 2009 H1N1 Influenza outbreak, studies showed marked reductions in the mortality rates of those treated with convalescent plasma. Treated patients also showed a decrease in the number of viruses in their system (viral load) within five days of symptom onset without severe adverse events occurring (i.e. difficulty breathing to the point where ventilation is required). 

Before the COVID-19 pandemic, CPT was also being studied to treat Ebola in several countries.


Canadian Blood Services. (n.d). COVID-19 and convalescent plasma. Retrieved from https://blood.ca/en/convalescentplasma

Mayo Clinic. (2020, May 20). Convalescent plasma therapy. Retrieved from



Schnur, M. B. (2020, April 18). Convalescent Plasma Therapy – Is it a Viable Treatment for

COVID-19?. Retrieved from https://www.nursingcenter.com/ncblog/april-


Featured image courtesy of Wix.

Article Contributors: Rahma Osman, Victoria Huang