Figure 3. The global distribution of clinical trials by phase (circles) and the centers carrying out research on COVID-19 plasma therapy (red bar) and their recruitment centers (cylinders). The main centers of each continent are highlighted in the enlarged image around the central map. Phase IV is indicated by green circle; phase III by blue circle, and phases II-III by red circle. The intercontinental collaborations of the clinical trial protocols at phase IV are represented by the dashed black lines on the world map.
