SIGLEC1 and susceptibility to pneumonia measurement: To analyze the association between CD169 RMFI and pneumonia status, the COV group was divided according to chest computed tomography (CT) images at the time of hospitalization and sampling: no pneumonia and non-interstitial pneumonia (None+P, n = 28), monolateral or minimal interstitial pneumonia (MiP, n = 6), and bilateral or severe pneumonia (BiP, n = 23).