The frequencies of anti-ACE2 IgM in these patients were very similar to the initial group: 11/38 (28.9%) of the patients with severe COVID-19 were positive for anti-ACE2 IgM antibodies compared with 1/14 (7.1%) in the group with milder COVID-19 (Supplemental Figure 1A, right panel). Here, ACE2 is linked to COVID-19.