MMP14 and COVID-19: As ageing is a primary risk factor of SARS-CoV-2 infection45,46 and membrane-bound MT1-MMP is found to be shed from the cell surface to produce a functional soluble form in both physiological and pathological events47–49, we therefore examined the concentrations of solACE2 and circulating MT1-MMP in plasma derived from young adults with average age of 29.2 years and the elderly with average age of 80.1 years.