The rise and fall of convalescent plasma therapy as a Covid-19 treatment

Early in the pandemic, scientists thought “convalescent plasma” might be a way to treat Covid-19.

By giving patients the plasma of people who had recovered (or convalesced) from Covid-19, the idea was this antibody-rich infusion would help their immune systems fight infection. It is a strategy tried, with various degrees of success, for other infectious diseases, including Ebola.

But growing evidence, including an international study published this week, shows convalescent plasma does not save lives of people critically ill with Covid-19. The researchers concluded the therapy was “futile”.

What’s convalescent plasma?

Convalescent plasma is a blood product containing antibodies against an infectious pathogen (such as SARS-CoV-2, the coronavirus that causes Covid-19). It comes from blood collected from people who have recovered from the infectious disease.

Scientists use a process called apheresis to separate the different blood components. Red and white cells and platelets are removed leaving plasma, which is rich in antibodies.

The very first Nobel Prize in Medicine (1901) was for diphtheria antitoxin, which is essentially a convalescent plasma transfusion. 🤯 https://t.co/ROkL3KueJh

— Jack Turban MD 🏳️‍🌈🧠 (@jack_turban) April 16, 2020

The story of convalescent plasma therapy (or serum therapy) originates in the 1890s. This is when physician Emil von Behring infected horses with the bacteria that causes diphtheria.

Once the horses recovered, Behring collected their antibody-rich blood to treat humans with the…

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