As shown in Figure S2C, SARS‐CoV‐2 infection downregulated the LL‐37 expression in all cell types; notably, macrophages from the normal, moderate to severe patients showed a gradient descent of LL‐37 expression, suggesting that the COVID‐19 severity was inversely proportional to the respiratory level of LL‐37. The gene discussed is CAMP; the disease is COVID-19.