* participants who are pregnant, breastfeeding, or have a positive pregnancy test result before enrollment * participants previously enrolled in the efprezimod alfa study * intubation for invasive mechanical ventilation is over 7 days * documented acute renal or hepatic failure * the investigator believes that participating in the trial is not in the best interests of the participant, or the investigator considers unsuitable for enrollment (such as unpredictable risks or subject compliance issues)

* participants who are pregnant, breastfeeding, or have a positive pregnancy test result before enrollment * participants previously enrolled in the efprezimod alfa study * intubation for invasive mechanical ventilation is over 7 days * documented acute renal or hepatic failure * the investigator believes that participating in the trial is not in the best interests of the participant, or the investigator considers unsuitable for enrollment (such as unpredictable risks or subject compliance issues)

participants who are pregnant, breastfeeding, or have a positive pregnancy test result before enrollment participants previously enrolled in the efprezimod alfa study intubation for invasive mechanical ventilation is over 7 days documented acute renal or hepatic failure the investigator believes that participating in the trial is not in the best interests of the participant, or the investigator considers unsuitable for enrollment (such as unpredictable risks or subject compliance issues)

participants who are pregnant, breastfeeding, or have a positive pregnancy test result before enrollment participants previously enrolled in the efprezimod alfa study intubation for invasive mechanical ventilation is over 7 days documented acute renal or hepatic failure the investigator believes that participating in the trial is not in the best interests of the participant, or the investigator considers unsuitable for enrollment (such as unpredictable risks or subject compliance issues)

- participants who are pregnant, breastfeeding, or have a positive pregnancy test result before enrollment - participants previously enrolled in the cd24fc study - intubation for invasive mechanical ventilation is over 7 days - documented acute renal or hepatic failure - the investigator believes that participating in the trial is not in the best interests of the participant, or the investigator considers unsuitable for enrollment (such as unpredictable risks or subject compliance issues)

- participants who are pregnant, breastfeeding, or have a positive pregnancy test result before enrollment - participants previously enrolled in the cd24fc study - intubation for invasive mechanical ventilation is over 7 days - documented acute renal or hepatic failure - the investigator believes that participating in the trial is not in the best interests of the participant, or the investigator considers unsuitable for enrollment (such as unpredictable risks or subject compliance issues)

1. patients who are pregnant, breastfeeding, or have a positive pregnancy test result before enrollment, 2. patients previously enrolled in the cd24fc study, 3. intubation for invasive mechanical ventilation is over 7 days, 4. documented acute renal or hepatic failure, 5. the investigator believes that participating in the trial is not in the best interests of the patient, or the investigator considers unsuitable for enrollment (such as unpredictable risks or subject compliance issues).

1. patients who are pregnant, breastfeeding, or have a positive pregnancy test result before enrollment, 2. patients previously enrolled in the cd24fc study, 3. intubation for invasive mechanical ventilation is over 7 days, 4. documented acute renal or hepatic failure, 5. the investigator believes that participating in the trial is not in the best interests of the patient, or the investigator considers unsuitable for enrollment (such as unpredictable risks or subject compliance issues).