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post covid-19 blood could hold the clue for a cure
while we wait for a vaccine, canada is set to try using the blood of covid-19 survivors to treat the seriously ill.
apr 27 2020
5 minute read
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at the speed covid-19 is spreading through the world, a vaccine may be the only way to stop it in its tracks. but as people continue to die, and experts say that a vaccine may be a whopping 18 months away, it’s worth looking into the past and see what kinds of stopgap measures could be a possibility as we wait.
convalescent plasma transfusion is a centuries-old treatment still used in hospitals today. after becoming infected and recovering from a virus, patients’ blood will have high numbers of in antibodies produced by their immune system. these antibodies bind to viruses and neutralize them. the hope when it comes to covid-19 is that giving antibody-infused blood plasma from a recovered donor to a newly sick person will help them develop an immune response and recover.
this form of passive immunity was first tried on diphtheria patients in the late 1800s, and has since been used to manage many diseases , including ebola, sars, and mers.
researchers and hospital sites across canada have just gotten approval to start collecting blood plasma for covid-19. they hope to see their first donors within a week. the initiative was the result of universities, researchers, and doctors across the country working around the clock to organize a trial. it took less than a month — an incredible feat that would normally take at least a year and a half, says dr. jeannie callum , a transfusion medicine specialist at sunnybrook health sciences centre and professor at the university of toronto.
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“there aren’t many of us transfusion medicine physicians across canada, so we’ve always worked collaboratively. that wasn’t a shock,” she says. “but every infection diseases doc, every critical care doc, every site, every research assistant, every university has basically stepped up to the plate to say, ‘how can we help?’ we only had our first call three weeks ago. we’re a very collaborative country and it would be nice for canada to offer something to the world. it’s something we can do because we have a national health system and a national blood supplier, it’s a great canadian opportunity.”
how do scientists find people with antibodies?
people who have been confirmed to have covid-19 and have since recovered are eligible. researchers will need 800 donors to serve 1,200 patients by the end of this year since each donor can donate four times — each time, their blood provides enough plasma for 1.5 patients. the best time to donate is the window between four weeks after your last symptom and 12 weeks after — the peak time for the highest number of antibodies.
people who have recovered from covid-19 can fill out an online registry at https://blood.ca/en/convalescentplasma or email blood4research@blood.ca with their contact information so canadian blood services can respond with details. researchers only want to hear from those who have been confirmed positive.
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“there’s a lot of people who think they had covid and want to have an antibody test,” says callum. “maybe you had a flu or cold in january. i get it, i’d love to know too if i’ve had covid, but we’re not offering that service.”
in the first tier of the trials, researchers are only looking at men’s blood.
“we’re not discriminating, it’s just that women have antibodies to other people’s tissue types because of pregnancy,” says callum. “even a one week pregnancy could give a person these antibodies. some pregnancies you might not even notice were happening and so we’re starting with men because they’ve never been pregnant.”
once researchers has reached a sufficient inventory and worked through the logistics, they will start to target women who have never been pregnant, and afterwards women who have been pregnant — but they’ll need to be tested for any antibodies.
potential risks involved
the most common issues with plasma donation is fluid overload , which can cause increased blood pressure and respiratory distress. however, there is less risk with covid-19 plasma donations because the amount given to patients is less than usual. typically, one litre is given to adult patients during blood transfusions, but only half a litre will be given to covid-19 patients in this trial.
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blood transfusions also normally happen very fast because the patient is bleeding. there’s less of a sense of urgency in covid-19 situations, and callum hopes the issue of fluid overload will be minimized by dripping blood more slowly into the patient.
other risks include allergic reactions, which manifests as itchy skin and hives. this happens about one per cent of the time and patients are generally treated with reactine or benadryl.
as for the concern of the spread of classic infections spread by blood, like hiv and hepatitis c, callum isn’t worried.
“those risks are so small we need mathematicians to calculate it,” she says. “we estimate that the risk of getting hiv from a blood transfusion is one in 21 million. we only transfuse a million products in canada per year, so that means once every 21 years, somebody might get exposed to hiv from a blood transfusion.”
however, because patients will be receiving convalescent plasma — not regular plasma — it is unknown how the antibodies being infused into covid-19 patients will interact with the virus in their bloodstream and lungs.
so far, a small study from china has reported improvement in severely ill patients and no adverse effects. another small study on five patients found promising results . researchers from the u.s. are running controlled trials to see whether patients who receive plasma recover faster than patients who don’t. south korea, france, and the u.k. are also currently running trials.
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“we’re going to be watching people very closely. every reaction to the blood product is recorded no matter how minor,” says callum. “basically, we’re starting this knowing nothing. we’ve seen small studies suggesting this is beneficial, suggesting patients have very high antibody levels but we otherwise know nothing. it’s going to be really fascinating.”
“who has the highest antibodies, is it random? and on the recipient side, does it make it difference if that donor had an off-the-chart antibody level versus average level versus below-average level? this study part of the analysis of the data. a lot of data is going to come out of this — not just ‘does the convalescent plasma work? yes or no.'”
diana duong is a writer and editor at healthing.@dianaduo.
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