The prognostic value of Clinical Frailty Scale in COVID-19 pneumonia across different pandemic phases: a comparison between the first and the fourth wave - Siniscalchi, Carmine; Ticinesi, Andrea; Guerra, Angela; Parise, Alberto; Cerundolo, Nicoletta; Prati, Beatrice; Simoni, Riccardo; Porro, Emanuela; Meschi, Tiziana (Frontiers in Medicine, 2025)