COVID-19 and convalescent plasma

Canadian Blood Services is proud to contribute again to an international clinical trial testing convalescent plasma as a possible treatment option for COVID-19. 

This time, the trial will assess if convalescent plasma from donors who have recovered from COVID-19 and who are vaccinated against the disease may be an effective treatment for patients who are immunocompromised and hospitalized with severe illness.   

Questions and answers: About the clinical trials

What is the purpose of this research?

The clinical trial will assess if convalescent plasma from donors who have recovered from COVID-19 and are vaccinated against the disease may be an effective treatment for patients who are immunocompromised and hospitalized with severe illness. While COVID-19 vaccines are widely available for most age groups, someone who is immunocompromised may not have a strong enough immune response after vaccination to protect them from becoming seriously ill if infected.  

In 2020, we supported similar clinical trials and the results showed convalescent plasma with a high level of antibodies against COVID-19 may benefit patients with immunodeficiency. The 2022 trial will further explore this. It will be an important contribution to research on a global scale that could help more patients in Canada and around the world.  

What is Canadian Blood Services’ role in the trial?

Canadian Blood Services is responsible for supplying convalescent plasma to all physicians caring for patients in Canada within the context of the clinical trial, under the authorization of Health Canada. Hema-Quebec will distribute convalescent plasma we collect to participating hospitals in Quebec.

As the national blood operator, we have the expertise and the infrastructure necessary to safely collect, prepare and distribute convalescent plasma for use in clinical trials.

Well-designed clinical trials, like the one we were involved with, help provide the information necessary to prove whether convalescent plasma may be an effective treatment for the most vulnerable patients here in Canada and around the world.

Which clinical trial is Canadian Blood Services collecting convalescent plasma for?

The trial we are supporting is called Clinical Trial for Convalescent Plasma for COVID-19: Randomized, Embedded, Multifactorial Adaptive Platform Trial for Community-Acquired Pneumonia (REMAP-CAP). Bacterial and viral infections, including COVID-19, are responsible for most cases of community-acquired pneumonia. 

More than 300 sites in 21 countries, including Canada, are participating in REMAP-CAP. Well-designed clinical trials, like this one, help provide the information necessary to prove whether convalescent plasma may be effective treatment option for patients who are immunocompromised and experiencing severe illness caused by COVID-19.  

To learn more about the trial, visit

In past trials, convalescent plasma was found to be ineffective in treating patients with COVID-19. Why are we participating in another trial?

While past studies we contributed convalescent plasma to, and others internationally, did not demonstrate sufficient benefit for the patients enrolled, the results did show COVID-19 convalescent plasma contains antibodies of different types, amounts and functions and that these antibodies can vary significantly from one donor to another. Therefore, there may be potential benefit from plasma with more antibodies compared to plasma with fewer antibodies.  

The timing of how quickly and frequently convalescent plasma is administered may also be a factor, as some studies have shown repeated transfusions earlier in patient care could lead to improved effects.  

And data from one of the studies we supported (REMAP-CAP) suggested that patients who were immunocompromised may benefit from convalescent plasma.    

The research team for this study (REMAP-CAP) is now investigating if plasma with higher levels of COVID-19 antibodies (convalescent plasma from donors who have recovered from and are vaccinated against the disease) transfused sooner could help patients who are immunocompromised recover from serious illness resulting from infection. Even if fully vaccinated for COVID-19, someone who is immunocompromised may not have a strong enough immune response after vaccination to protect them.

When is the trial happening?

Canadian Blood Services will resume collecting convalescent plasma in November 2022 for use at all participating hospitals in Canada. We will continue collecting convalescent plasma donations until the clinical trial investigators in Canada confirm they have the supply needed to complete their research. 

When will the results from the trials be available?

Generally, clinical trial results are known after a trial is complete and the research team has been able to analyze the full dataset from the trial. It can take several months before a research team is ready to publish the results. 

If it works, will Canadian Blood Services collect convalescent plasma long term?

The clinical trial needs to be completed first, so we have evidence that this therapy actually works. Internationally, researchers continue to develop and investigate various options to treat, prevent or cure COVID-19. At this time, it is too early to say what could happen or what our role may be longer term.

Questions and answers: Donors

Who can donate convalescent plasma?

You may be eligible to donate convalescent plasma for the clinical trial if:   

  • You tested positive for COVID-19.
  • You have been vaccinated against COVID-19.
  • You meet Canadian Blood Services’ current eligibility criteria for plasma donation
  • You can attend a participating Canadian Blood Services’ blood donor centre.

At this time, we are focusing on donors who have not experienced a past pregnancy, which can increase the risk of transfusion-related acute lung injury (TRALI) in patients.  

I’ve had COVID-19 and am vaccinated against it and want to help. How can I donate for the trial?

At this time, previous COVID-19 convalescent plasma donors from the studies which ran in 2020 and 2021 who are vaccinated will be asked to donate in support of this new study. We may recruit donors in other ways, if needed.

How many donors will be needed for the clinical trial?

We estimate we will need to collect approximately 200 units (~250 ml. per unit) of convalescent plasma for the REMAP-CAP trial. Convalescent plasma will be collected through our multi-plasma donor program, in which we can collect up to three units of plasma in one donation. Multi-plasma donors can also donate as often as every 14 days.

Depending on the amount collected per donor and the needs of the patients involved, we estimate roughly 20–50 convalescent plasma donors are needed to support the clinical trial.

Where will we collect convalescent plasma?

We will collect convalescent plasma at our Vancouver, Calgary, Edmonton, Saskatoon, Regina, Winnipeg, London, Hamilton, Toronto, Ottawa, Halifax, Saint John and Charlottetown blood donor centres.

I have donated convalescent plasma. Is there a way to find out my antibody levels against COVID-19?

No, Canadian Blood Services only uses this information to determine whether donors meet the requirements to participate in this clinical trial.

There are different tests for COVID-19 antibodies. For this trial, we measure a subset of the antibodies someone has. Our testing tells us the level of your antibodies at the time of your donation; however, research shows that antibodies to COVID-19 wane over time, which is why public health officials recommend booster doses of the current vaccines.

My convalescent plasma donation doesn’t qualify for the clinical trial. Will my donation be used in another way?

If your plasma donation meets Canadian Blood Services’ regular eligibility requirements but does not meet the REMAP-CAP clinical trial requirement (does not contain enough COVID-19 antibodies), it may be processed for other patients in need as outlined in our brochure, called What happens to your donation.

Questions and answers: patients

Who is immunocompromised?

There are many reasons someone is or may become immunocompromised. For example: 

  • Cancer treatment
  • Having a stem cell transplant (within the last two years)
  • Receiving chimeric antigen receptor (CAR)-T-cell therapy (a treatment to help the immune system attach to and kill cancer cells)
  • An organ transplant requiring medication that suppresses the immune system
  • Moderate or severe primary immunodeficiency (e.g., DiGeorge syndrome, Wiskott-Aldrich syndrome)
  • Advanced or untreated HIV infection
  • Active treatment with high-dose corticosteroids or other medications that can suppress immune response

How are patients being selected for the trial?

Patient participation in the trial will be determined by their treating physician in consultation with the patient and according to the clinical trial protocol.

Is convalescent plasma safe for patients?

Yes. Since 2020, data collected on the use of COVID-19 convalescent plasma through various studies around the world — some of which Canadian Blood Service participated in — has shown it is safe for patients to receive. Today’s research is now focused on how and when COVID-19 convalescent plasma is administered and whether it may be an effective treatment for some patient populations (e.g., patients who are immunocompromised).