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 Sunday 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.

Swaminathan says WHO still considers convalescent plasma therapy to be experimental and said it should continue to be evaluated. She added that the treatment is difficult to standardise, since people produce different levels of antibodies and the plasma must be collected individually from recovered patients. Swaminathan says that the studies have been small and provided low-quality evidence.  She says 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.