Plasma therapy still 'experimental'
The World Health Organisation says using plasma from the recovered to treat COVID-19 is still considered an experimental therapy and that the preliminary results showing it may work are still inconclusive. President Donald Trump on 23 August 2020 approved an emergency authorisation of convalescent plasma for COVID-19 patients.
WHO's chief scientist Dr Soumya Swaminathan said convalescent plasma therapy has been used in the last century to treat numerous infectious diseases, with varying levels of success.
- WHO still considers convalescent plasma therapy to be experimental and said it should continue to be evaluated.
- The treatment is difficult to standardise, since people produce different levels of antibodies and the plasma must be collected individually from recovered patients. The studies have been small and provided low-quality evidence.
- Countries can do an emergency listing if they feel the benefits outweigh the risks but that that's "usually done when you're waiting for the more definitive evidence.
- Dr Bruce Aylward, a senior adviser to WHO's director-general, said that convalescent plasma therapy can come with numerous side effects, from a mild fever and chills to more severe lung-related injuries.
- Convalescent plasma therapy involves transfusion of the blood plasma of recovered patient into another patient.
- 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 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.
- According to the Textbook of Medical Physiology by Guyton and Hall, Temporary immunity can be achieved in a person without injecting any antigen.
- This is done by infusing antibodies, activated T cells or both obtained from the blood of someone else or from some other animal that has been actively immunised against these antigens.