inclusion criteria: is willing and able to, or has a legally acceptable representative who is willing and able to, provide informed consent to participate and to cooperate with all aspects of the protocol. is male or female, age ≥18 years is hospitalized with covid-19 pneumonia with a diagnosis of sars-cov-2 infection confirmed by reverse transcriptase polymerase chain reaction (rt-pcr) or equivalent local test within 14 days of randomization. has pao2/fio2 ratio of ≤200 (or equivalent spo2/fio2 ratio ~235 within 24 hours before randomization. this ratio may be adjusted based on altitude.

inclusion criteria: is willing and able to, or has a legally acceptable representative who is willing and able to, provide informed consent to participate and to cooperate with all aspects of the protocol. is male or female, age ≥18 years is hospitalized with covid-19 pneumonia with a diagnosis of sars-cov-2 infection confirmed by reverse transcriptase polymerase chain reaction (rt-pcr) or equivalent local test within 14 days of randomization. has pao2/fio2 ratio of ≤200 (or equivalent spo2/fio2 ratio ~235 within 24 hours before randomization. this ratio may be adjusted based on altitude.

inclusion criteria: 1. is willing and able to, or has a legally acceptable representative who is willing and able to, provide informed consent to participate and to cooperate with all aspects of the protocol. 2. is male or female, age ≥18 years 3. is hospitalized with covid-19 pneumonia with a diagnosis of sars-cov-2 infection confirmed by reverse transcriptase polymerase chain reaction (rt-pcr) or equivalent local test within 14 days of randomization. 4. has pao2/fio2 ratio of ≤200 (or equivalent spo2/fio2 ratio ~235 within 24 hours before randomization. this ratio may be adjusted based on altitude.

inclusion criteria: 1. is willing and able to, or has a legally acceptable representative who is willing and able to, provide informed consent to participate and to cooperate with all aspects of the protocol. 2. is male or female, age ≥18 years 3. is hospitalized with covid-19 pneumonia with a diagnosis of sars-cov-2 infection confirmed by reverse transcriptase polymerase chain reaction (rt-pcr) or equivalent local test within 14 days of randomization. 4. has pao2/fio2 ratio of ≤200 (or equivalent spo2/fio2 ratio ~235 within 24 hours before randomization. this ratio may be adjusted based on altitude.