It will be difficult "to find and diagnose them in this vanishingly small window," said Dr. Ilan Schwartz, an infectious disease doctor at the University of Alberta who was not involved in the study. "The study looks solid, but it isn't exactly practical in the real world."
Plasma has additional logistical hurdles, said Dr. Titanji from Emory University. Treatment is given as an intravenous infusion – a process that requires skilled hands – and patients must be monitored afterward. That might be easier in long-term care facilities, but far more difficult to achieve for the general population, she said.
And plasma may not work as well as monoclonal antibody therapy – a synthetic preparation that is made en masse in the lab and not drawn from human blood, and that focuses on just one or two types of antibody at a time, rather than the total amount produced naturally by the immune system. Two types of monoclonal antibody treatments have been approved for emergencies in Covid patients.
But plasma has some advantages over monoclonal antibody treatments, emphasized Dr. Polack.
Because monoclonal antibodies are synthetic and tedious to make, they come at a high price, sometimes costing thousands of dollars (although the US government has prepaid some doses). The limited supply chain of treatment, as well as unexpectedly low demand, have made it inaccessible to many patients in need in the US and abroad.
In countries like Argentina, plasma could be one of the best treatment options available, said Dr. Polack. Plasma infusions in Buenos Aires cost less than $ 200 per patient. "It's more accessible, cheaper and more universal," he said.
Even in the US, plasma "really is the only game in town that is widely available in terms of antibody therapy," said Dr. Wang from Stanford.
Instead of viewing monoclonal antibodies as an upgrade for convalescent plasma, "they each have a different place in the armor," said Dr. Pirofski. "Anything this virus can control is really an incredible benefit at this point."