A medical procedure doctors have used to treat novel diseases for a century has emerged as a focal point in the fight against Covid-19: convalescent plasma.
Conva-what-now…?
Convalescent plasma is the term used for plasma that is removed from the blood of a person who has recovered from a disease, then transfused into a patient still battling it.
Yes, it sounds a little confusing. So allow us to break down everything you need to know about convalescent plasma — and why it matters right now.
OK, first: What, exactly, is plasma?
Let’s start with a little biology lesson. I promise it’ll be fun.
Plasma is the liquid part of your blood. It’s light yellow, and made up of about 91 percent to 92 percent water. It accounts for around 55 percent of your blood, with the other 45 percent being red blood cells, white blood cells and platelets. (Platelets help your blood clot.)
Here’s why we’re talking about it now: When your body is exposed to a foreign pathogen, your body’s response is to produce antibodies, “which are proteins that can bind to the virus and help to deactivate it, clear it from circulation and prevent it from invading the body’s cells,” according to Dr. Jeffrey Jhang, medical director of clinical laboratories and transfusion services for the Mount Sinai Health System in New York.
Those antibodies — your internal army working to vanquish foreign invaders — are contained in plasma. And once you’ve recovered, or convalesced, from a given virus, those antibodies stick around in your plasma for a certain amount of time, ready to fight that virus if it comes back. That length of time varies, and each virus requires its own antibodies, meaning that SARS antibodies, for example, are powerless to stop MERS.
But here’s the thing: Your soldiers can sometimes fight for other people. Doctors can extract convalescent plasma from a recovered patient, then transfuse it into a patient who is fighting the disease you recovered from. This means your antibodies may help that person’s own immune system in its war against the disease by accelerating the time it takes to develop its own army of antibodies.
However, before we get too excited, it’s important to note that when it comes to Covid-19, we don’t actually know yet if our antibody soldiers can fight for other people. More on that below.
Wait, that’s crazy. Has this worked before?
Yes! Doctors have been using convalescent plasma transfusions to help patients fight diseases as far back as the Spanish Flu of 1918. More recently, the procedure has been used in patients with SARS, Ebola, H1N1 and more.
The name for this therapy is passive immunity. When you develop your own antibodies — say, through a vaccine — that’s active immunity. But when you “borrow” them from another person via convalescent plasma, it’s passive. This has been used when no other treatment options are available, and studies have suggested that it can help improve the condition of patients still suffering from various diseases, including H1N1 and SARS.
“Convalescent plasma has historically been used therapeutically and for prophylaxis” — as prevention — “typically in times when a new disease, virus, bacteria comes on the scene and we don’t have any viral-specific therapies for that new or novel disease,” said Dr. Erin Goodhue, executive medical director of the American Red Cross.
What is particularly noteworthy about using convalescent plasma to treat Covid-19 is that the treatment has never been used as widely as is now being proposed, Dr. Goodhue said. This means that, for the first time, the medical and scientific communities will be able to conduct the type of rigorous studies of the procedure itself to better determine its effectiveness. That type of study hasn’t been possible in previous uses of the treatment.
It is also used to treat burn, trauma and cancer patients — a plasma explainer from the New York Blood Center calls it “liquid gold.”
So … does it work for Covid-19?
Remember when I said not to get too excited yet?
As we learned from our biology lesson earlier, once a person recovers from Covid-19, his or her blood — more specifically, his or her plasma — contains antibodies that can fight the virus. Since this coronavirus is novel — no one had been exposed to it before this outbreak — our bodies don’t already contain the antibodies needed to fight it.
The medical community is racing to determine whether convalescent plasma will help those still battling Covid-19. But it’s simply too soon to know conclusively whether it works — the Food and Drug Administration only announced its initiative to collect convalescent plasma about a month ago. Some hospitals got a small jump on that, but it will likely be months before we have a definitive answer, experts said.
“I’ve heard anecdotes of some patients improving, but I don’t have any results of any kind of rigorous nature to be able to share,” Dr. Jhang said.
Dr. Goodhue echoed Dr. Jhang’s caution in drawing conclusions, but said there are encouraging signs.
“I’m still continuing to hear positive anecdotal evidence,” Dr. Goodhue said. “But to balance that out, there have been some cases where it just hasn’t seemed to work for a patient at all, unfortunately.”
Still, more convalescent plasma donations means more opportunities to study its effectiveness. As of Wednesday, about 35,000 people have reached out to Mount Sinai, in New York, to see if they are candidates; about 6,000 have been screened for antibodies; and more than 1,000 high-antibody producers have been identified. Mount Sinai has given plasma to more than 150 people and counting, according to a spokeswoman.
The Red Cross has “distributed a couple hundred convalescent plasma products, and is projected to collect and process hundreds more this week,” according to a spokeswoman. It is collecting donations at more than 170 locations nationwide, with more on the way. Thousands of potential donors have reached out to the organization, but less than 10 percent have met the F.D.A.’s eligibility requirements for donation.
Is the donation process painful? Is it safe?
That’s an easy one: no, and yes — so long as you’re OK with the prick of a needle.
The process takes between an hour-and-a-half and two-and-a-half hours. Though it’s somewhat similar to a normal blood donation — particularly the screening process during which donors are asked questions about their health history — there are significant differences.
In a typical blood donation, a phlebotomist inserts a needle into a vein in your arm. That needle is connected to a hose, and that hose is connected to a bag. Your heart does the work here and pumps your blood into that bag, with the usual donation amount being about a pint.
A plasma donation, however, is like a closed-loop system.
It starts the same as a regular blood donation, with a phlebotomist inserting a needle into an arm vein. But instead of your blood being pumped into a bag, it is drawn into a machine with a centrifuge, where the plasma is separated from the blood. The plasma is collected in a separate bag, and the blood that was drawn is returned to your body with a saline solution through the needle already in your arm. This process repeats a few times until the proper amount of plasma is collected, which varies based on weight. Side-effects are mostly similar to a normal blood donation, so you might feel a little faint or dizzy, but in most cases that’s about it. (Your body will replenish the lost plasma in a day or two.)
A single donation can result in two to four units of plasma, each of which can be transfused into an ill patient. Exactly what happens to your plasma after donation depends on where you donate, but it will undergo tests to identify transmittable diseases, per F.D.A. regulations. Eventually it will end up being used to treat Covid-19 patients.
I’ve recovered from Covid-19. How can I donate?
To qualify, donors must pass normal blood-donation requirements and be symptom-free of Covid-19 for at least 14 days, and, in most cases, must have positive results from a test. (Other restrictions may apply, depending on the organization.)
I had Covid-19 symptoms and recovered, but was never tested. Can I donate?
Unfortunately, probably not. The F.D.A.’s eligibility criteria include a positive diagnosis of Covid-19, along with being symptom-free for at least 28 days before donation; or at least 14 days without symptoms and a negative Covid-19 test.