ACE2 and COVID-19: ACE2 receptors mediate SARS‐CoV‐2 into cells, suggesting a critical link between ACE2, immune system, inflammation, and cardiovascular disease.[6] Comparing with the receptor‐binding domain (RBD) of SARS‐CoV, several residual changes in the SARS‐CoV‐2 RBD increase its ACE2 binding affinity.[7] What's more, the antigenicity of SARS‐CoV and SARS‐CoV‐2 is significantly different.[8] COVID‐19 spreads quickly worldwide and causes diseases of varying degrees.