- Plasma injected into hospitalised Covid-19 patients may protect them from developing severe disease or requiring a ventilator
- This theory is currently being tested in clinical trials
- The procedure is a 'stopgap' that can be used while there still are no drugs or vaccines to effectively combat the disease.
The blood plasma of people who have recovered from the new coronavirus infection may help critically ill Covid-19 patients recover, a new study finds.
Of 25 sick patients given plasma transfusions, 19 improved and 11 left the hospital, the researchers reported. None of the patients had side effects from the transfusion.
"While physician-scientists around the world scrambled to test new drugs and treatments against the Covid-19 virus, convalescent serum therapy emerged as potentially one of the most promising strategies," explained lead researcher Dr James Musser, chair of the department of pathology and genomic medicine at Houston Methodist Hospital. "With no proven treatments or cures for Covid-19 patients, now was the time in our history to move ahead rapidly."
Plasma transfusions from recovered patients have been used since at least 1918 during the Spanish Flu pandemic and in 2003 in the SARS (severe acute respiratory syndrome) pandemic. It was also employed in the influenza H1N1 pandemic in 2009 and the 2015 Ebola outbreak in Africa, the researchers noted.
The new report was published online recently in the American Journal of Pathology.
This latest study isn't the only research looking into the power of plasma transfusions in treating Covid-19.
Two groups of researchers are testing the theory in clinical trials.
One study, from doctors at NYU Grossman School of Medicine, Montefiore Health System and Albert Einstein College of Medicine in New York City, will try to determine whether "convalescent plasma" injected into hospitalised COVID-19 patients can protect them from developing severe disease or requiring a ventilator.
Meanwhile, researchers at the Johns Hopkins Bloomberg School of Public Health in Baltimore are poised to launch a pair of new studies looking at the use of plasma in healthcare workers and those who are sick at home with Covid-19.
Dr Corita Grudzen, vice chair for research in NYU Langone Health's department of emergency medicine, wrote the study protocol for the New York City study.
Liquid part of the blood
"What we hope to see is that convalescent plasma, used at this stage of disease, so early on, prevents patients from dying, from going on a mechanical ventilator, or any sort of bad outcome," Grudzen said in a HealthDay Live interview.
The tactic is "sort of a stopgap measure in the sense that, when you don't have a vaccine, it's something that can be used in a new infection where we don't have known drugs or other therapeutics or biologics that we know can work against the disease," Grudzen explained.
Exactly what is blood plasma?
"Blood plasma is the liquid part of the blood," explained Dr Arturo Casadevall, chair of Hopkins' department of molecular microbiology and immunology and lead researcher on the two Hopkins studies.
Characterised by its yellowish cast, plasma contains both red and white blood cells, as well as the colourless platelets the body deploys to clot and stem bleeding from wounds or cuts.
"And that's [also] where the antibodies are," Casadevall noted. "The antibodies are floating in the liquid."
Not without dangers
With plasma therapy, he explained, "you're taking the antibodies that somebody else made when they recovered and you're transferring them to a new person. So, the new person gets them already made, and can use them right away."
Convalescent plasma is not without dangers.
The two main ones are the patient catching an infectious disease, though blood screening helps to lessen that possibility, or a patient's immune system reacting badly to the injected plasma of another person. Grudzen noted that, "especially in older people, it's a little more risky".
And Casadevall cautioned that plasma therapy still needs to be tested on Covid-19 to see if it'll work against this specific virus, "simply because it's a new organism."
To that end, Hopkins is set to start two Covid-19 plasma investigations simultaneously, with funding coming from Bloomberg Philanthropies, the state of Maryland, and Hopkins.
"The first trial is focused on trying to use plasma on high-risk populations," he noted. That investigation will include healthcare workers on the frontlines of the pandemic and nursing home residents, with a minimum of 150 participants.
"The second trial is focused on people who are sick at home," Casadevall said. "We know most people recover. Most people today who are sick are sitting at home hoping to get better. But we also know that some fraction of them will get worse," he added.
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