TABLE 1.

Factors involved in age‐related differences of SARS‐CoV‐2 pathogenesis

Factors involved in age‐related differences of SARS‐CoV‐2 pathogenesis	Adults	Children	References
Expression of ACE2 receptor and TMPRSS2	↑	↓	96, 98, 136
Comorbidities and medications	↑	↓	99, 100, 101, 102
Innate immune responses	↓	↑	103
Adaptive immune responses	↑	↓	72, 109
Pre‐existing antibodies to other HCoVs	↑	↓	104, 109
Trained immune responses	↓	↑	125, 126
ADE and macrophage hyperactivation	↑	↓	106, 117, 119
Cytokine storm	usually ↑	usually ↓(except for MIS‐C)	80, 121, 122
Vitamin D and other micronutrients	↓	↑	127, 130

SARS‐CoV‐2, severe acute respiratory syndrome coronavirus 2; ACE2, angiotensin‐converting enzyme 2; TMPRSS2, transmembrane protease serine 2; HCoVs, human coronaviruses; ADE, antibody‐dependent enhancement; MIS‐C, multisystem inflammatory syndrome in children.