Doctors using ‘convalescent plasma therapy’ to treat COVID-19
Plasma is the matrix on which the blood cells float. It also houses crucial components of immunity known as antibodies. Antibodies are the immediate warriors who fight an invading pathogen – an antigen – to defeat it. Once that is done, some blood cells function as memory cells so that they can identify and defeat the same enemy if and when it invades again by quickly producing the same antibodies
Convalescent blood products (CBP), obtained by collecting whole blood or plasma from a patient who has survived a previous infection and developed humoral immunity against the pathogen responsible for the disease in question, are a possible source of specific antibodies of human origin.
Convalescent plasma therapy banks on the age-old concept of passive immunity when antibodies for some diseases, such as diphtheria, were developed in horses and injected into humans. Active immunity is what is achieved by introducing an attenuated pathogen (such as the BCG vaccine) into the body to generate an immune response. The other kind of immunity is passive immunity.
Use of Therapy in COVID-19:
- Convalescent plasma therapy is an important method for effectively treating patients with severe and critical symptoms
- The therapy aims to use the antibodies in the convalescent plasma to minimise the presence of the virus in patients
- Donors must be recovered patients who are up to the standard for being discharged from hospital.
- Only plasma will be collected while red blood cells, white blood cells and blood platelets will be transfused back into the donor’s bod
- As the disease develops, the body has already begun developing antibodies against the virus. Infusing convalescent plasma is essentially like topping with more antibodies hoping that increased amount of antibodies will dampen the disease progression
- The special prerequisites as given by The Central Drugs Standard Control Organisation while considering convalescent plasma include ABO compatibility and cross-matching of the donor plasma. The recipient should be closely monitored for several hours post transfusion for any transfusion-related adverse events and use should be avoided in patients with IgA deficiency or immunoglobulin allergy.
The dose is variable ranging from 4 ml/kg to 13 ml/kg (usually 200-ml single dose given slowly over not less than two hours), it added.
What is Convalescent Plasma-Therapy? Has it been used before?
It has been tried for several diseases, most recently for Ebola. The WHO had issued a detailed guidance document for its use in the wake of the Ebola outbreak, to be used as an “empirical treatment modality”. While there is no proven treatment available for Ebola virus disease (EVD), whole blood collected from patients in the convalescent phase of infection has been used as an empirical treatment with promising results in a small group of EVD cases.
- People who have recovered from COVID-19 disease would have antibodies against the virus. Infusing the antibodies to critically ill patients is expected to improve the chances of survival. The plasma that is transfused contains the antibodies.
- Treatment with convalescent plasma is a classical, time-tested method. It has been used against measles, chickenpox, and rabies.
- Convalescent plasma has been proven “effective and life-saving” against other infectious diseases, including rabies and diphtheria