inclusion criteria: * recent (≤2weeks prior to randomization) confident diagnosis of covid-19 confirmed by antigen detection and/or pcr (polymerase chain reaction), and/or seroconversion or any other emerging and validated diagnostic test * in some patients, it may be impossible to get a confident laboratory confirmation of covid-19 diagnosis after 24h of hospital admission because viral load is low and/or problems with diagnostic sensitivity. in those cases, in absence of an alternative diagnosis, and with highly suspect bilateral ground glass opacities on recent (\<24h) chest-ct scan (confirmed by a radiologist and pulmonary physician as probable covid-19), a patient can be enrolled as probable covid-19 infected. in all cases, this needs confirmation by later seroconversion. * presence of acute hypoxic respiratory failure defined as (either or both) * saturation below 93% on minimal 2 l/min o2 * pao2/fio2 below 300 * admitted to specialized covid-19 ward * age 18-80 * male or female * willing to provide informed consent

inclusion criteria: * recent (≤2weeks prior to randomization) confident diagnosis of covid-19 confirmed by antigen detection and/or pcr (polymerase chain reaction), and/or seroconversion or any other emerging and validated diagnostic test * in some patients, it may be impossible to get a confident laboratory confirmation of covid-19 diagnosis after 24h of hospital admission because viral load is low and/or problems with diagnostic sensitivity. in those cases, in absence of an alternative diagnosis, and with highly suspect bilateral ground glass opacities on recent (\<24h) chest-ct scan (confirmed by a radiologist and pulmonary physician as probable covid-19), a patient can be enrolled as probable covid-19 infected. in all cases, this needs confirmation by later seroconversion. * presence of acute hypoxic respiratory failure defined as (either or both) * saturation below 93% on minimal 2 l/min o2 * pao2/fio2 below 300 * admitted to specialized covid-19 ward * age 18-80 * male or female * willing to provide informed consent

inclusion criteria: - recent (≤2weeks prior to randomization) confident diagnosis of covid-19 confirmed by antigen detection and/or pcr (polymerase chain reaction), and/or seroconversion or any other emerging and validated diagnostic test - in some patients, it may be impossible to get a confident laboratory confirmation of covid-19 diagnosis after 24h of hospital admission because viral load is low and/or problems with diagnostic sensitivity. in those cases, in absence of an alternative diagnosis, and with highly suspect bilateral ground glass opacities on recent (<24h) chest-ct scan (confirmed by a radiologist and pulmonary physician as probable covid-19), a patient can be enrolled as probable covid-19 infected. in all cases, this needs confirmation by later seroconversion. - presence of acute hypoxic respiratory failure defined as (either or both) - saturation below 93% on minimal 2 l/min o2 - pao2/fio2 below 300 - admitted to specialized covid-19 ward - age 18-80 - male or female - willing to provide informed consent

inclusion criteria: - recent (≤2weeks prior to randomization) confident diagnosis of covid-19 confirmed by antigen detection and/or pcr (polymerase chain reaction), and/or seroconversion or any other emerging and validated diagnostic test - in some patients, it may be impossible to get a confident laboratory confirmation of covid-19 diagnosis after 24h of hospital admission because viral load is low and/or problems with diagnostic sensitivity. in those cases, in absence of an alternative diagnosis, and with highly suspect bilateral ground glass opacities on recent (<24h) chest-ct scan (confirmed by a radiologist and pulmonary physician as probable covid-19), a patient can be enrolled as probable covid-19 infected. in all cases, this needs confirmation by later seroconversion. - presence of acute hypoxic respiratory failure defined as (either or both) - saturation below 93% on minimal 2 l/min o2 - pao2/fio2 below 300 - admitted to specialized covid-19 ward - age 18-80 - male or female - willing to provide informed consent