In the absence of vaccines or antiviral drugs, researchers at Johns Hopkins University in Baltimore say the key to slowing and treating the coronavirus might be hidden in the blood of those who’ve already recovered from the disease.

The method of using “convalescent serum” — essentially harvesting virus-fighting antibodies from the blood of previously infected patients — dates back more than a century, but has not been used widely in the United States in decades.

During the Spanish flu epidemic of 1918, scientists reported that transfusions of blood products obtained from survivors led to a 50 percent drop in deaths among severely ill patients. A similar strategy was used to treat and slow the spread of polio and measles outbreaks decades ago, but the technique fell out of favor in the 1950s with the innovation of modern vaccine science and antiviral drugs, said Dr. Arturo Casadevall, chair of the molecular microbiology and immunology department at the Johns Hopkins Bloomberg School of Public Health.

When Casadevall learned in December that a new coronavirus was spreading rapidly in China, he started telling colleagues that it might be time to revive the antiquated treatment.

“I’m an infectious disease doctor who is interested in history,” Casadevall said. “I knew the history of what was done in the early 20th century with epidemics. They didn’t have vaccines then, they didn’t have any drugs then — just like the situation we face now. But physicians then knew that, for certain conditions, you could take the blood of the immune and use it to prevent disease or treat those who became ill.”

In a paper published Friday in the Journal of Clinical Investigation, Casadevall and a colleague, Dr. Liise-anne Pirofski, argued that collecting blood serum or plasma from previously infected people might be the best hope for treating severe cases of COVID-19, the disease caused by the virus, at least until a better treatment can be developed.

There’s some evidence from recent history that suggests the approach could work.

In 2003, doctors in China used plasma from recovered patients to treat 80 people suffering from the viral disease known as severe acute respiratory syndrome, or SARS — an earlier coronavirus — and found that the treatments were associated with improved outcomes and shorter hospital stays. In 2014, the World Health Organization published guidelines for using donated plasma to treat people infected with Ebola after the treatments showed promise.

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In an interview with Stat News last month, a top Food and Drug Administration official said convalescent plasma might be helpful in the fight against the new coronavirus. Although the treatment is not a cure, Casadevall says it might be an important stopgap.

Researchers in the U.S. and across the globe have been scrambling to develop drugs for the coronavirus, but federal officials say those treatments are likely months or — in the case of a vaccine — more than a year away. That leaves hospitals with few options other than ventilators to treat COVID-19 patients suffering from respiratory failure, stoking concerns nationally that a surge of severely ill patients in the coming weeks could overwhelm emergency rooms and intensive care units.

“The approach definitely has merit, and what’s remarkable about it is it’s not a new idea; it’s been with us for a good hundred years or longer,” said Dr. Jeffrey Henderson, an assistant professor of medicine and molecular microbiology at the Washington University School of Medicine in St. Louis. “I think we don’t know until we have experience and case reports with this particular disease whether it will be effective, but just based on its track record with a number of other viruses, I think it has a very good chance of working.”

Henderson said part of what makes the treatment attractive is its simplicity. Although there is danger in giving a patient the wrong type of blood, safety advancements over the past two decades have made adverse outcomes rare. And hospitals have the tools needed to begin harvesting and transfusing patients with blood serum right away, he said.

The Johns Hopkins team is planning to submit its plan for approval by the FDA, but Casadevall said they don’t anticipate problems since the method has been used in the past and relies on standard blood-banking technology. He hopes to begin collecting serum from recovered patients within four to six weeks.

Patients tend to make large numbers of antibodies against an infecting pathogen, and these antibodies often circulate in the blood of survivors for months or years afterward. By collecting and transfusing a survivor’s serum or plasma — the liquid portion of blood left once cells and platelets have been removed — doctors could potentially boost an ailing patient's immune response, Casadevall said.

Doctors in China have begun treating COVID-19 patients with plasma harvested from survivors and have reported somewhat positive results, especially when the method is applied early in the disease, though it has not been tested widely.

“The usage of plasma will probably reduce the time needed to treat the disease from five to 10 days to three to five days,” said Dr. Zhang Wenhong, the leader of a medical team sent from Shanghai to Wuhan to help tackle the outbreak, in an interview with Al-Jazeera last week.

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Casadevall argues that convalescent serum could also be given to front-line health care workers to help protect them from becoming ill.

To implement his plan, academic hospitals would need to work collaboratively with blood banks to set up research protocols and treatment guidelines. Doctors at Johns Hopkins started that work weeks ago, Casadevall said, and they have begun drafting guidelines that can be copied by hospitals across the country.

He’s already been in touch with doctors at the Mayo Clinic in Minnesota, he said.

“At the local level, hospitals and blood banks have everything they need to do this,” Casadevall said. “But what would really help is coordination from the federal government.”

First, Casadevall said, the U.S. must immediately begin widespread testing, because it’s impossible to collect blood serum from survivors if public health officials don’t know who’s been infected. Second, Casadevall said federal officials may need to oversee the interstate shipment of blood products. He can imagine a scenario where blood banks in Seattle, which has been at the epicenter of the U.S. outbreak for weeks, might be in a position to send excess blood products to other cities where outbreaks are still ramping up.

And finally, Casadevall said, government officials would need to help spread the word. He believes people who’ve had the coronavirus and recovered will be eager to donate plasma if they believe it could help elderly patients and health care workers.

“This is by no means a panacea,” Casadevall said. “But at a time when the message has been, ‘There’s nothing you can do but wash your hands,’ this is an opportunity to do something proactive that can help fight this.”