Vitamin D Serum Levels in Subjects Tested for SARS-CoV-2: What Are the Differences among Acute, Healed, and Negative COVID-19 Patients? A Multicenter Real-Practice Study oleh Luca Gallelli, Gaia Chiara Mannino, Filippo Luciani, Alessandro de Sire, Elettra Mancuso, Pietro Gangemi, Lucio Cosco, Giuseppe Monea, Carolina Averta, Pasquale Minchella, Manuela Colosimo, Lucia Muraca, Federico Longhini, Antonio Ammendolia, Francesco Andreozzi, Giovambattista De Sarro, G&P Working Group, Erika Cione