This is a multicenter, randomized, initially blinded (masked), phase 2 trial to assess SARS-CoV-2 vaccination reactions in two populations:

To evaluate safety and explore clinical benefits of Silmitasertib 1000 mg BID dose in patients with severe illness caused be SARS-COV-2.

To assess safety and efficacy of immunotherapy with delivery of of natural killer cells in treatment of patients with moderate COVID-19 disease.

To evaluate the safety and tolerability of REGN10933+REGN10987 compared to placebo

Performance (discrimination / calibration) of models [ Time Frame: From date of study enrollment until the date of first documented ARDS diagnosis or date of death from any cause, whichever comes first, assessed up to study end (estimated at 3 months). ] Performance (discrimination / calibration) of models that predict the risk of development of ARDS and/or mortality among COVID-19 patients who

Primary Outcome Measures  :

1. Primary endpoint: Venous or arterial thrombotic events [ Time Frame: 28 days or until hospital discharge, whichever earlier ]

   Hierarchical composite: Death due to venous or arterial thrombosis, pulmonary embolism, clinically evident DVT, type 1 MI, ischemic stroke, systemic embolism or acute limb ischemia, or clinically silent DVT