Specifically, we identified three markers, apolipoprotein E (APOE), membrane-spanning 4-domain subfamily A member 4A (MS4A4A), and protein-tyrosine kinase 2-beta (PTK2B), which displayed the same trend in AD and COVID-19 compared to the control group according to our AD-high-risk scores (Figure 4C). Here, APOE is linked to COVID-19.