Research on COVID-19 is advancing at unprecedented speed, but a strategy that doctors are considering to treat COVID-19 patients seems more archaic than innovative. Caregivers in hospitals in the United States use century-old convalescent plasma therapy – draining the blood of survivors and injecting it back into the sick.
This is because the hundreds of research papers published in the past few months and the record leaps in vaccine development have not been fast enough to keep up with the blistering speed of the current pandemic. People are sick and dying now, which is why doctors are turning to plasma therapy as an interim measure they hope to be able to help in the time before other treatments go online.
“I think it’s a bridge, until we can develop a vaccine or a pharmaceutical product whose safety and efficacy can be demonstrated and which can be produced in large quantities”, explains Elliott Bennett-Guerrero , who is studying the use of this product. convalescent plasma in COVID-19 patients at Stony Brook Medicine.
Once someone is infected with a virus like the new coronavirus and recovers, their blood is rich in antibodies produced by their immune system to help them fight the virus. Doctors hope giving donated blood plasma to a newly sick person, who may not have the antibody yet, may help them heal faster.
“With plasma, we take advantage of the body’s incredible ability to develop antibodies and immunity against pathogens,” says Bennett-Guerrero. “We are transferring these protective factors to people who are sick and have not been able to trigger an immune response.”
It has been used as a treatment since at least the 1890s, when the blood of survivors was donated to patients with diphtheria. Studies during the 1918 flu pandemic showed that it was an effective treatment. It has been used to manage dozens of diseases over the past century, including measles and chickenpox.
Now doctors hope it can help people with COVID-19. Preliminary data from a handful of patients in China have shown that their condition improves after receiving a plasma infusion from survivors, but there is still insufficient data to say for certain that it works. Researchers in the United States are conducting controlled studies to see if patients who receive plasma improve faster than those who do not.
“This is an old technique,” said Scott Koepsell, medical director of the transfusion and transplant support services division at the University of Nebraska Medical Center, which collected plasma from survivors of Ebola. He says that if plasma transfusions have been used for more than a century, it is still a treatment of last resort. “It’s a really well-intentioned approach, but it has a lot of variability and limits. “
For example, each person who survives an infection will have a slightly different mixture of immune substances in their plasma. Each plasma-treated patient then receives a slightly different treatment. This can make it very difficult for researchers to say whether plasma therapy is generally effective (or ineffective) or whether it depends on whether a patient gets a very good (or bad) lot of plasma. Medical researchers are trying to solve this problem by only allowing survivors with high levels of antibodies to donate plasma, but the plasma will always vary from donor to donor.
In addition to the general uncertainty about the effectiveness of these transfusions, there are also risks for any transfusion of blood plasma: serious side effects may include lung damage and allergic reactions.
In the United States, Koepsell treated Ebola patients with convalescent plasma during the 2014 and 2015 epidemics. With Ebola, unlike COVID-19, there were additional benefits: plasma can also help prevent dangerous bleeding caused by this virus. The Ebola virus was more likely to be dangerous for everyone who contracted it, he said, making the risks easier to justify in the absence of clear evidence of the effectiveness of plasma transfusions.
In any epidemic, convalescent plasma has one major advantage: it is available as soon as someone survives a new disease. “The good thing is that it is readily available soon after something has happened,” says Koepsell.
Ideally, other more standardized drugs specific to this disease would also be readily available. These other drugs are still taking too long to reach patients – in part because there have not been enough investments to develop them. After the outbreaks of SARS and MERS, which are also coronaviruses, scientists have started work on possible treatments and vaccines. But with more distance from these epidemics, the money dried up. The researchers doing this work are not as close to the answers as they could have been had there been more sustained investment.
It is possible to narrow the window between the time a new disease appears and the time treatments are available, says Koepsell, so that doctors don’t keep looking for plasma. An investment in disease preparedness and constant work on antiviral drugs against pathogens like coronaviruses would give them more resources for the next epidemic.
“We hope that governments and institutions will recognize that pandemics can occur more frequently,” he said. “I would like to avoid collecting blood and transfusing it every time a new disease occurs. “