These proteins that only show an age-dependency in COVID-19 patients but not in the general population point toward age-dependent differences in host response patterns to SARS-CoV-2, and include markers involved in inflammation (SERPINA3, ITIH4, SAA1, SAA1, SAA2, ITIH3, CFB, C7, and AHSG), lipid metabolism (APOC1, APOC2, APOC3, APOB, and APOD), and coagulation (KLKB1, and FBLN1). Here, SERPINA3 is linked to COVID-19.