We’ve gotten used to a life of restricted menu options during this pandemic, an analogy that extends all the way to our treatment if we contract COVID-19. But there’s an item still on the list at most medical institutions, and if it strikes you as familiar, it should: It’s been around – and working – for more than a century.

Convalescent plasma therapy, in fact, is promising enough that it’s something you and your doctor may want to consider if you’re sick and hospitalized. It’s got history, it isn’t very risky (more on that in a moment), and, however sadly, the pool of potential plasma donors to fight coronavirus in the U.S. is growing rapidly.

You may not have heard the term “convalescent plasma” in full, but chances are it still rings a bell. That’s the power of celebrity. Tom Hanks, Rita Wilson, and George Stephanopoulos are among the well-known Americans who’ve donated plasma after recovering from COVID-19, and they’ve advocated for other recovered patients to do the same.

Here’s the gist of the concept: Plasma is the yellow portion of the blood that contains antibodies, which we use to fight infection. A person who has already recovered from COVID-19 often has developed such antibodies, according to recent data. Thus, injecting that person’s plasma into an ill individual may help boost the immune system, avert a tragic end, and speed recovery.

It is hardly new. Convalescent plasma has been used to treat bacterial and viral infections going back to diptheria outbreaks in the 1890’s and the Spanish Flu in 1918. In recent decades, the tactic was used to fight H1N1 influenza, SARS, and Ebola outbreaks with some documented success.

With treatment options lacking right now, plasma infusions merit a close look. We’ve had so many people – more than 1.3 million – become infected and then recover in the U.S. that the potential donor base is large. Currently, the treatment is being offered primarily to those who are seriously or critically ill, with more than 31,000 patients receiving the plasma. Multiple studies show that it appears to be a safe therapy.

The historical medical literature is encouraging, from a review of Spanish influenza pneumonia patients decades ago to a trial of 80 patients with SARS in Hong Kong, where those treated with convalescent plasma before day 14 of their infection had almost four times better outcomes – and three times better survival rates – than patients receiving plasma later. Though some of this research is limited by poor design or lack of randomization, it offers some precedent for investigating plasma and its potential efficacy.

Multiple studies have demonstrated that plasma infusions reduce the amount of virus in the blood, although I should point out that not all have shown a mortality benefit, including a recent meta-analysis of severe influenza patients and an Ebola trial. But what about COVID-19, you ask?

The best answer: It’s promising, and it’s early.

The first reported use of convalescent plasma to treat COVID-19, in five critically ill patients in Wuhan, China, resulted in the patients’ clinical status improving, with three of them coming off ventilators and being discharged. In a second Chinese study, all ten patients with severe illness not only improved clinically, but also had higher oxygenation levels and demonstrated positive changes in their lung scans. Recent reports from Italy indicate lower mortality rates with plasma use in COVID-19 patients there. Not all the studies are failsafe, mind you, but these recent returns are good.

A small, non-peer-reviewed study from Mount Sinai Hospital found that 39 severely ill, COVID-19 individuals who received convalescent plasma experienced better outcomes than patients not given the treatment. In fact, preliminary data suggest that nearly half as many patients died in the plasma group as in the control group. Getting the treatment earlier in the disease course appears to be important; the researchers did not find a benefit in more critically ill patients, who already had been placed on ventilators in the ICU. By that point, the horse may have already left the barn, rendering plasma therapy less effective.

At Houston Methodist hospitals, 25 patients with severe or life-threatening cases of COVID-19 were provided plasma, and within two weeks, more than three-quarters of them showed some degree of improvement. And a very recently published randomized control trial of 103 severely ill patients in Wuhan, though it did not reach statistical significance, trended toward better outcomes in the convalescent plasma group versus the standard treatment group.

Convalescent plasma has become a hot commodity. Twenty countries in Europe are using or plan to use it. In the U.S., physicians from 57 institutions established the National COVID-19 Convalescent Plasma Project to better investigate its use to treat the virus.

As we surpass 11 million cases and 530,000 deaths worldwide from COVID-19, we face an immediate and unprecedented challenge. With the data limitations noted, I believe the literature gives us hope that plasma treatment can make an immediate difference. In fact, it may be one of our most promising therapy options available right now, along with steroids and proning patients.

Better-designed trials are already underway, looking at plasma’s use both in severe and less severe cases, and as a form of prevention in individuals who are exposed to the virus, like health care workers. In a world of limited options, this oldie could prove golden.

Carolyn Barber is an emergency physician.

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