Sargramostim in Patients With Acute Hypoxic Respiratory Failure Due to COVID-19 (SARPAC)

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 Exclusion Criteria: * Patients with known history of serious allergic reactions, including anaphylaxis, to human granulocyte-macrophage colony stimulating factor such as sargramostim, yeast-derived products, or any component of the product. * mechanical ventilation before start of study * patients with peripheral white blood cell count above 25.000 per microliter and/or active myeloid malignancy * patients on high dose systemic steroids (\> 20 mg met…