U Blood-Banking Experts Explain How Convalescent Plasma Can Be Used to Treat COVID-19

Submitted by: U of M Medical Students, Eric Nagarajan, BS, and Sid Kanwar, BS

Over 22,000 Minnesotans have tested positive for COVID-19, according to the Minnesota Department of Health, with about 70% of these patients making a full recovery. Increasing numbers of recovered patients statewide has sparked discussions about the use of antibodies as a therapy for those with recent infections. We sought details from two University of Minnesota Medical School experts to shed light on the issue and what it could mean for the state.

What is convalescent plasma? 

Convalescent plasma refers to the antibodies that are present in the plasma of people who have recovered from an infection. 

“These antibodies can be passively transferred [from recovered patients] to sick patients to neutralize the virus,” said Claudia Cohn, MD, PhD, associate professor in the Department of Laboratory Medicine and Pathology and chief medical officer of the American Association of Blood Banks.

Convalescent plasma is different from a vaccine, which offers active immunity. While vaccines induce the body’s immune response to create antibodies to fight a pathogen, passive antibody therapy can deliver a donor’s antibodies directly through transfusion. These antibodies can neutralize some of the virus, decreasing the overall viral load for the patient’s immune system. While convalescent plasma does not offer full immunity to the recipient, it has the potential to aid in their recovery. 

Dr. Cohn referenced the use of passive antibody therapy in past viral outbreaks, saying, “In the 2009 H1N1 pandemic, convalescent plasma was shown to reduce mortality and in Ebola … it showed significantly longer survival in some patients.”

How is convalescent plasma being used to treat COVID-19?

The Mayo Clinic, along with dozens of other hospital systems, has received approval for an expanded access program to use convalescent plasma for patients who have severe or life-threatening disease or for those with a risk of progression to severe disease. COVID-19 Convalescent Plasma (CCP) is considered an investigational drug by the FDA, which limits its use more ubiquitously.

“It is not a licensed blood component, [so] patients can receive it in a study. More recently, the National Expanded Access Treatment Protocol was put in place, which allows patients to obtain CCP after being registered. Patients with severe enough disease to require hospital admission will likely qualify,” Dr. Cohn said.

All CCP comes from donors who have recovered from laboratory-proven COVID-19, and Dr. Cohn says every donation has the potential to save three lives.

How effective is CCP to treat COVID-19?

“When evaluating a new therapy, it is best to have an equipoise and a truly dispassionate approach to testing to see if the benefits outweigh the risks,” said Jed Gorlin, MD, adjunct professor in the Department of Laboratory Medicine and Pathology and co-director of Transfusion Medicine at Hennepin Healthcare and Children’s Hospitals and Clinics of Minnesota. “The vast majority has been used in one-armed trials.” 

At this point, support for CCP is indirect or anecdotal. Surrogate studies with SARS and MERS have associated convalescent plasma with a drop in viral load, or the amount of virus measurable in a patient’s test sample.

“SARS and MERS are our poster-children for bad coronaviruses,” Dr. Gorlin said.

He says a drop in viral load should make it easier for the body to fight off disease, but it’s not known how effective this therapy is or when it should be used. 

“We don’t know who, how or how much, or when to treat,” he said. 

Evidence suggests CCP has the most benefit for patients within the first 10 days of the disease and for those with risk factors for severe disease, such as age, sex and history of respiratory disease.

How safe is it to receive a unit of CCP? 

Safety is paramount when transferring blood products, especially to those with compromised immune and lung statuses. Receiving a unit of CCP is safer than receiving a unit of blood as plasma has the same screening protocols as blood and avoids the risks of red blood cell incompatibility. Dr. Gorlin speaks about the concern of transfusion-related acute lung injury (TRALI), which he describes as “not very likely” given pre-screening at-risk populations for specific antibodies that appear to correlate with the risk of TRALI. Modern blood banking techniques make inadvertently transferring infectious agents or causing transfusion reactions low.

“The risk of giving one unit of plasma is minimal, and as far as specifics, we’re learning after the fact,” Dr. Gorlin said.

How do I know if I can donate?

Those who have evidence of infection with COVID-19 and have been symptom-free for 14 days can donate convalescent plasma for treatment and research.

Although previously the necessity of laboratory proof for COVID-19 infection was a major obstacle due to the shortage of tests, antibody tests are now available and offered at all blood centers.

Blood donation centers, such as those associated with American Red Cross and Memorial Blood Centers, are equipped to accept donations of convalescent plasma by appointment.

What about standard blood donations?

Dr. Cohn has been keeping a keen watch on the blood supply on a national scale and within the M Health Fairview system. Blood donation centers have transitioned to blood donations by appointment, with reduced mobile drives to maintain social distancing and ensure donor safety. Thankfully, Dr. Crohn says the blood supply is currently sufficient, at least within M Health Fairview.

“Blood donors turn out with an upswing of altruism when there is a crisis,” Dr. Cohn said, crediting the surge of generous donors who have responded. Other measures by the hospitals, such as cancelling elective surgeries and adjustments to thresholds for giving transfusions, have resulted in a 30% decrease in red blood cell use and a 50% decrease in platelet use.

The altruism of donors will need to continue in the coming months, however, especially with a peak in COVID-19 cases expected this summer.

“Blood has a limited shelf life,” Dr. Cohn said. “The need for blood is constant.”

Readers are encouraged to sign up for appointments to donate blood several weeks out as many sites currently have limited capacity.

Where can I donate?

If you have recovered from COVID-19 with evidence of infection and are willing to donate convalescent plasma, please contact Memorial Blood Centers or the American Red Cross to schedule an appointment.

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