Doctors first tried injecting patients with blood plasma in the early 1900s. The method has been used against diphtheria, the 1918 flu pandemic, measles and Ebola.
The authorizations mean, effectively, that the agency believes the treatments in question are promising and largely safe, though there’s not yet definitive data supporting their efficacy.
One trend that seems to be emerging from the data we do have is that, similarly to a lot of antiviral drugs, earlier administration of the treatment is more likely to be of benefit.
Many options are being explored to treat COVID-19. These include new drugs specifically designed to target SARS-CoV-2, as well as “repurposed” drugs - that is, existing drugs designed to treat a different disease. By far the oldest treatment being tested, though, is convalescent plasma.
The therapy was once considered the most promising approach by the WHO.
Convalescent plasma therapy is a passive immunisation process. It is simply the transfusion of plasma containing antibodies from immune survivors of infectious diseases to the affected individuals. Plasma is a light yellowish fluid which makes more than half of the blood’s volume. Passive immunisation in general, could be either natural or acquired.
Convalescent plasma collected from recovered patients has been a therapeutic modality employed for over a hundred years for various infectious pathogens. Specifically, it has been used in the treatment of many viral infections with varying degrees of clinical efficacy. As we consider the use of convalescent plasma in the battle against this new strain of coronavirus, it is prudent to review what is known from past experiences.
The transfusion of up to 500 ml of convalescent plasma with unknown levels of neutralizing antibodies in 84 patients with confirmed EVD was not associated with a significant improvement in survival.
Drawn from survivors, the stuff comes enriched in antibodies that could help to fight off the disease—but it also has the potential to carry other diseases, like malaria, that are common in west Africa where Ebola is raging. The new system will kill off any extra contaminants that may be lurking in this potentially live-saving serum.
In the past, plasma therapy has been a weapon against the 1918 flu, polio, measles, rabies, hepatitis B and Ebola — with varying levels of success. More recently, it showed some promise in treating other coronaviruses like SARS and MERS, particularly when given to a patient early in their illness.
If the FDA’s emergency authorizations aren’t used responsibly, they could lose their power.
“Convalescent plasma has historically been used therapeutically and for prophylaxis” — as prevention — “typically in times when a new disease, virus, bacteria comes on the scene and we don’t have any viral-specific therapies for that new or novel disease,” said Dr. Erin Goodhue, executive medical director of the American Red Cross.