Convalescent Plasma Therapy for COVID-19: A Graphical Mosaic of the Worldwide Evidence

In this mini-review, experts from Mayo Clinic and other leading institutions argue that during a health emergency such as a pandemic, evidence originating from multiple levels of the epistemic evidence hierarchy should be used to inform policy and health care decisions. The authors analyzed data from randomized clinical trials and matched-control studies as well as other clinical evidence from sources worldwide to better understand the value of convalescent plasma for treating COVID-19.

Salient points include:

  • Randomized clinical trials have demonstrated a survival benefit of COVID-19 convalescent plasma when patients are transfused early in the course of the disease, but these studies generally show limited or no benefit later, when patients require greater supportive therapies. Such trials have also revealed that convalescent plasma transfusion contributes to a reduced symptom set and better viral clearance.
  • In contrast, matched-control studies generally showed a survival benefit associated with convalescent plasma therapy.
  • Aggregation and meta-analysis of data from 16 studies — both randomized clinical trials and matched-control studies — that presented the survival data using a Kaplan-Meier diagram revealed a directionally consistent pattern whereby convalescent plasma transfusion was generally associated with greater patient survival.
  • The authors discuss several possible reasons for differences between the results from randomized clinical trials and matched-controlled studies, including specific limitations in trial procedures, bias risk and variations in the quality of the plasma administered.

Additionally, the article presents the principles of convalescent plasma therapy, its historical use in infectious disease medicine, and experimental evidence for and clinical limits to its value in treating COVID-19.