The treatment injects antibody-rich plasma from people who have recovered from the novel coronavirus into people who have severe cases of COVID-19, the disease caused by the virus. Antibodies are proteins in blood that fight specific bacteria and viruses.

In the absence of a vaccine, doctors and scientists are looking to so-called convalescent plasma because they consider it low risk and because it has been effective during past epidemics.

Now they have to find out if it works against the new strain of coronavirus.

On March 27, the Journal of the American Medical Association published an article about five critically ill patients with COVID-19 in Shenzen, China, all of whom improved after receiving convalescent plasma transfusions. Another study of 10 patients in Wuhan, China, reported that all symptoms disappeared or significantly improved within one to three days of a plasma transfusion.