Convalescent plasma therapy for severe SARS-CoV-2

Atreatment which involves antibodies donated by people who have recovered from a coronavirus infection is helping thousands of patients worldwide who are severely ill with COVID-19.

Worldwide there are over 60 clinical trials actively recruiting Covid-19 patients to study the effect of socalled “convalescent plasma.” Plasma is the cell-free liquid part of blood after the removal of all red and white blood cells and platelets.

Mount Sinai Hospital in the US has used the therapy on more than 20 critically ill coronavirus patients. Johns Hopkins Bloomberg School of Medicine in Baltimore, Maryland, is also conducting convalescent plasma trials, as is Britain’s Guy’s and St Thomas’ hospital in London. Greece recently started trials at the Attiko and Evangelismos hospital in Athens.

India’s three states with the highest number of Covid-19 cases -- Maharashtra, Tamil Nadu and Delhi -- have also sought permission from the Council of Medical Research

to conduct convalescent plasma therapy tests. The plasma from the blood of a recovered Covid-19 patient is rich in antibodies -- proteins secreted by immune cells called B lymphocytes, or B cells, to target a pathogen such as SARS-Cov-2 for destruction.

One cured person’s plasma can produce two doses of the transfusion material. Critically ill patients receive 200-400ml of plasma intravenously, and their progress is then carefully monitored.

While vaccination provides life-long immunity, in the case of passive antibody therapy, the effect lasts only so long as the injected antibodies remain in the blood.

The therapy was first used over a century ago in 1918 during the Spanish flu pandemic.

The most recent instance of the use is the 2018 Ebola outbreak.

It was used in the H1N1 epidemic of 2008-2009, on SARS which broke out in 2003 and MERS in 2012.

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