31 March 2020
Critically ill patients with COVID-19 have shown improvement after transfusion of plasma from patients who have recovered from the disease.
Plasma is the straw-coloured liquid component of blood that transports the blood cells. It contains proteins, including antibodies.
The survivors’ plasma is rich in specific antibodies that their immune system has developed to fight a particular infection. And these antibodies can confer short-term immunity when given to another person.
Using so-called ‘convalescent plasma’ from disease survivors to treat currently infected patients is not new. This process of passive immunisation where a patient is given antibodies from someone who has recovered from an infection was used as far back as the 1918 influenza pandemic.
And now, 2 separate research teams have reported promising results from small trials of convalescent plasma in patients with COVID-19.
In one study in Shenzhen, China, 5 patients with COVID-19 were given convalescent plasma by transfusion. The patients had severe pneumonia, were being treated with antivirals and were on ventilators. After receiving the convalescent plasma, all patients had an improvement in symptoms and within 10 days, 4 of the 5 patients no longer required ventilation.
The second study (from Wuhan, China) gave convalescent plasma to 10 severely ill patients with COVID-19. Their clinical symptoms were significantly improved within 3 days. The virus was not detectable in 7 of the 10 patients who previously had had virus detectable in the bloodstream.
In an editorial in the Journal of the American Medical Association (JAMA), experts discuss the limitations of the Shenzhen study, including that there was no control group who did not receive the plasma, for comparison. Another limitation was that the patients were receiving other therapies at the same time. Despite this, they suggest there is merit in evaluating convalescent plasma in more rigorous trials of patients with COVID-19.
The Food and Drug Administration in the USA has approved emergency use of convalescent plasma for seriously ill COVID-19 patients, while clinical trials evaluate its safety and effectiveness before it may be deployed more widely.
Approval has been sought in Britain for trials of convalescent serum to treat COVID-19.
