Abstract: nutrients Article Effectiveness of In-Hospital Cholecalciferol Use on Clinical Outcomes in Comorbid COVID-19 Patients: A Hypothesis-Generating Study Sandro Giannini 1, * , Giovanni Passeri 2 , Giovanni Tripepi 3 , Stefania Sella 1 , Maria Fusaro 1,4 , Gaetano Arcidiacono 1 , Marco Onofrio Torres 1 , Alberto Michielin 1 , Tancredi Prandini 1 , Valeria Baffa 1 , Andrea Aghi 1 , Colin Gerard Egan 5 , Martina Brigo 6 , Martina Zaninotto 7 , Mario Plebani 7 , Roberto Vettor 8 , Paola Fioretto 8 , Maurizio Rossini 9 , Alessandro Vignali 2 , Fabrizio Fabris 1 and Francesco Bertoldo 6 1 2 3 4 5 6



 Citation: Giannini, S.; Passeri, G.; 7 8 Tripepi, G.; Sella, S.; Fusaro, M.; Arcidiacono, G.; Torres, M.O.; 9 Michielin, A.; Prandini, T.; Baffa, V.; et al. Effectiveness of In-Hospital * Clinica Medica 1, Department of Medicine, University of Padova, 35128 Padova, Italy; stefania.sella@unipd.it (S.S.); dante.lucia11@gmail.com (M.F.); gparcidiacono91@gmail.com (G.A.); marcoonofrio.torres@studenti.unipd.it (M.O.T.); alberto.michielin89@gmail.com (A.M.); tancredi.prandini@gmail.com (T.P.); valeria.baffa@gmail.com (V.B.); andrea.aghi@gmail.com (A.A.); fabrizio.fabris@unipd.it (F.F.) Unit of Clinica e Terapia Medica, Department of Medicine and Surgery, University of Parma, 43126 Parma, Italy; giovanni.passeri@unipr.it (G.P.); alessandro.vignali@gmail.com (A.V.) National Research Council (CNR), Institute of Clinical Physiology (IFC), Clinical Epidemiology of Renal Diseases and Hypertension, Ospedali Riuniti, 89124 Reggio Calabria, Italy; gtripepi@ifc.cnr.it National Research Council (CNR), Institute of Clinical Physiology (IFC), 56124 Pisa, Italy CE Medical Writing, 56021 Pisa, Italy; colingegan@gmail.com Internal Medicine, Department of Medicine, University Hospital AOUI, 37134 Verona, Italy; martina.brigo@gmail.com (M.B.); francesco.bertoldo@univr.it (F.B.) Laboratory Medicine Unit, Department of Medicine, University of Padova, 35128 Padova, Italy; marti.zaninotto@libero.it (M.Z.); mario.plebani@unipd.it (M.P.) Clinica Medica 3, Department of Medicine, University of Padova, 35128 Padova, Italy; roberto.vettor@unipd.it (R.V.); paola.fioretto@unipd.it (P.F.) Rheumatology Unit, Department of Medicine, University of Verona, 37134 Verona, Italy; maurizio.rossini@univr.it Correspondence: sandro.giannini@unipd.it; Tel.: +39-049-8212169 Cholecalciferol Use on Clinical Outcomes in Comorbid COVID-19 Patients: A Hypothesis-Generating Study. Nutrients 2021, 13, 219. https://doi.org/10.3390/nu13010219 Received: 16 December 2020 Accepted: 11 January 2021 Published: 14 January 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ Abstract: Little information is available on the beneficial effects of cholecalciferol treatment in comorbid patients hospitalized for COVID-19. The aim of this study was to retrospectively examine the clinical outcome of patients receiving in-hospital high-dose bolus cholecalciferol. Patients with a positive diagnosis of SARS-CoV-2 and overt COVID-19, hospitalized from 15 March to 20 April 2020, were considered. Based on clinical characteristics, they were supplemented (or not) with 400,000..