Given that mucins are shed from SARS-CoV-2–infected respiratory epithelial cells (10), as shown in our study (Figure 8B and Supplemental Figures 2 and 4), and can enter the circulation via mucosal barrier injury (10), establishing blood mucin expression profiles associated with disease presentation and severity and response to therapy will hold great potential to battle this COVID-19 pandemic. This evidence concerns the gene MUC5AC and COVID-19.