inclusion criteria: * covid-19 confirmed by a positive rt-pcr test * hospital admission within 11 days from the onset of symptoms * spontaneous breathing with oxygen requirement ≥1 l/min * expected discharge \> 96 hours at randomization

inclusion criteria: * covid-19 confirmed by a positive rt-pcr test * hospital admission within 11 days from the onset of symptoms * spontaneous breathing with oxygen requirement ≥1 l/min * expected discharge \> 96 hours at randomization

inclusion criteria: covid-19 confirmed by a positive rt-pcr test hospital admission within 11 days from the onset of symptoms spontaneous breathing with oxygen requirement ≥1 l/min expected discharge > 96 hours at randomization

inclusion criteria: covid-19 confirmed by a positive rt-pcr test hospital admission within 11 days from the onset of symptoms spontaneous breathing with oxygen requirement ≥1 l/min expected discharge > 96 hours at randomization

inclusion criteria: 1. covid-19 confirmed by a positive rt-pcr test 2. hospital admission within 11 days from the onset of symptoms 3. spontaneous breathing with oxygen requirement ≥1 l/min 4. expected discharge > 96 hours at randomization

inclusion criteria: 1. covid-19 confirmed by a positive rt-pcr test 2. hospital admission within 11 days from the onset of symptoms 3. spontaneous breathing with oxygen requirement ≥1 l/min 4. expected discharge > 96 hours at randomization