There have not been randomized clinical trials that compare the treatment to a placebo to provide answers to some questions, such as when doctors should administer plasma, what the correct dosage is and if it will work.
Two infectious disease specialists in a conference call this week called the use of convalescent plasma promising, but said more study is needed and each is involved in study currently.
The treatment is called passive immunization and uses antibodies from plasma of people who have recovered from the coronavirus. Doctors now have the ability to obtain the plasma, package it and share it through established blood-banking procedures. The technique has been successful in patients with rabies and with hepatitis B.
Passive immunization gives the body an immediate supply of potentially protective antibodies doctors suspect that it is most affective when given early at a time with a lower viral load in the patient but there are still questions to be answered about the procedure.
“I don’t have all the data that went into the decision to go into the emergency authorization,” said Dr. Shmuel Shoham, associate director of Transplant and Oncology Infectious Disease program at Johns Hopkins University School of Medicine. “What everybody agrees on though, is that the gaps in the knowledge that exist can be addressed by high-quality randomized control trials, where you compare people who receive high-antibody plasma to those who receive control plasma.”
That testing is being done at Johns Hopkins and about 30 other centers around the country to find the answers to questions, and establish how best to treat coronavirus patients with convalescent plasma.
Shoham said that historically the highest impact of passive immunization happens in combination with a vaccine. “That happens when someone has exposure to hepatitis B or rabies, but at this point we don’t have a vaccine for the coronavirus so what we’re left with is looking at how effective passive immunization in the form of convalescent plasma is.”
Dr. Liise-anne Pirofski, chief of the Department of Medicine, Division of Infectious Diseases at Albert Einstein College of Medicine and Montefiore Medical Center, was right in the heart of the coronavirus pandemic this spring in New York City when she helped design a study on the efficacy of convalescent plasma on coronavirus patients.
Both studies are in the early stages and still need volunteers.
“There have been signals of the efficacy of convalescent plasma in pandemics going back over a hundred years, and I think the important aspects of the data that are available, that deserve consideration, are that there appears to be a dose response of the plasma,” Pirofski said. “The units of plasma that had more antibodies appear to be more effective, which is something we looked for in the use of our development of any sort of drug or therapeutic.”
Pirofski also reiterated what Shoham said in that early administration of the treatment leads to a more positive outcome. “I will also mention that there are a large number of case reports and observational studies in the public domain that demonstrate positive signals when convalescent plasma is used,” she said. “A report from China suggested that in patients that were desperately ill and treated early,those viral loads seem to have decreased graphically upon administration of plasma.”
