References
Niveditha Devasenapathy, Zhikang Ye, Mark Loeb, et al. Efficacy and safety of convalescent plasma for severe COVID-19 based on evidence in other severe respiratory viral infections: a systematic review and meta-analysis. CMAJ 2020;10.1503/cmaj.200642.
I believe that the best use for convalescent plasma would be in passive immunization of at risk populations like seniors in residential care.
The amount of antibodies in convalescent plasma is fixed and not active so it is likely inadequate to neutralize the large number of virus particles in an infected patient. However convalescent plasma would have the potential to neutralize a few virus particles in early illness before replication gets too far. We know this from using passive immunization in other viral disease, like Gama globulin for Hep A. Lets not forget our medical history to guide our new therapy.
I would hope that Conversant plasma for passive immunization is being studied for prophylaxis.