Efprezimod Alfa (CD24Fc, MK-7110) as a Non-antiviral Immunomodulator in COVID-19 Treatment (MK-7110-007)

Inclusion Criteria:

• Diagnosed with coronavirus disease 2019 (COVID-19) and confirmed severe acuterespiratory syndrome coronavirus 2 (SARS-coV-2) viral infection
• Severe or critical COVID-19, or National Institute of Allergy and Infectious Diseases (NIAID) 8-point ordinal score 2, 3 or 4 (Scale 2: requiring invasive mechanicalventilation or extracorporeal membrane oxygenation (ECMO); Scale 3: non-invasiveventilation or high flow oxygen devices; Scale 4: supplemental oxygen support; aperipheral capillary oxygen saturation (SpO2) </= 94% or tachypnea (respiratory rate >/= 24 breaths/min). Intubation should be within 7 days

Exclusion Criteria:

• Participants who are pregnant, breastfeeding, or have a positive pregnancy test resultbefore 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 interestsof the participant, or the investigator considers unsuitable for enrollment (such asunpredictable risks or subject compliance issues)