Fig 2. Participation of acute care facilities in the US Expanded Access Program (EAP) for convalescent plasma stratified by US hospital referral region.

Choropleth map displaying the number of participating acute care facilities that enrolled patients in the EAP within each hospital referral region—a geographical region that represents a catchment region of patients who get healthcare at similar facilities. Lower numbers of participating acute care facilities are displayed in a lighter hue of blue, and higher numbers of participating acute care facilities are displayed in a darker hue of blue. Hospital referral regions with 0 participating acute care facilities are displayed in grey. Hospital referral regions are not defined in US territories; thus, the choropleth map does not display data from Puerto Rico, the US Virgin Islands, Guam, or the Northern Mariana Islands. The base layer of the geographical map was retrieved from the Dartmouth Atlas Project (https://data.dartmouthatlas.org/supplemental/#boundaries) [32].