In particular, there were 2 studies showing the opposite:
The 1st study shows a positive outcome for patients:
"Effect of Convalescent Plasma on Mortality among Hospitalized Patients with COVID-19: Initial Three-Month Experience"
The 2nd study shows even a worsening:
"Convalescent plasma in the management of moderate COVID-19 in India: An open-label parallel-arm phase II multicentre randomized controlled trial (PLACID Trial)"
As usual, we looked into the studies, and found that there is not only a different outcome, but also a mentionable difference in when the therapy had been applied. Emphasizing that the evidence is low regarding all treatments for COVID-19, in comparison to all available treatments, the early application of plasma therapy seems quite promising.
For details of our analysis regarding the efficacy and safety of the treatments for COVID-19, you can REGISTER under rampmedical.com. EU-awarded and free access.