MTOR and infection: Low dose mechanistic target of rapamycin (mTOR) inhibitors was shown to reduce rates of infection and improved immunity and response to influenza vaccination in elderly [44,45]; consistently, metformin that inhibits the mTOR pathway and activates 5′-AMP-activated protein kinase (AMPK) as well as lowers blood glucose levels has been proposed to hamper severe SARS-CoV-2 infection in elderly [46].