Efficacy and Safety Study of IV Ravulizumab in Patients With COVID-19 Severe Pneumonia

Inclusion Criteria: 1. Males or female participants ≥ 18 years of age and ≥ 40 kilograms at the time of providing informed consent. 2. Confirmed diagnosis of severe acute respiratory syndrome coronavirus 2 infection (for example, via polymerase chain reaction and/or antibody test) presenting as severe COVID-19 requiring hospitalization. 3. Severe pneumonia, acute lung injury, or acute respiratory distress syndrome confirmed by computed tomography or X-ray at Screening or within the 3 days prior to Screening, as part of the participant's routine clinical care. 4. Respiratory distress requiring mechanical ventilation, which can be either invasive (requiring endotracheal intubation) or noninvasive (with continuous positive airway pressure or bilevel positive airway pressure). 5. Female participants of childbearing potential and male participants with female partners of childbearing potential must follow protocol specified contraception guidance for avoiding pregnancy for 8 months after treatment with the study drug. Exclusion Criteria: 1. Participant was not expected to survive for more than 24 hours. 2. Participant was on invasive mechanical ventilation with intubation for more than 48 hours prior to Screening. 3. Severe pre-existing cardiac disease (that is, New York Heart Association Class 3 or Class 4, acute coronary syndrome or persistent ventricular tachyarrhythmias). 4. Participant had an unresolved Neisseria meningitidis infection. 5. Used the following medications and therapies: * Current treatment with a complement inhibitor or * Intravenous immunoglobulin within 4 weeks prior to randomization on Day 1 6. Treatment with investigational therapy in a clinical study within 30 days before randomization, or within 5 half-lives of that investigational therapy, whichever was greater. Exceptions: * Investigational therapies were allowed if received as part of BSC through an expanded access protocol or emergency approval for the treatment of COVID-19. * Investigational antiviral therapies (such as remdesivir) were allowed even if received as part of a clinical study. 7. Female participants who were breastfeeding or who have a positive pregnancy test result at Screening. 8. History of hypersensitivity to any ingredient contained in the study drug, including hypersensitivity to murine proteins. 9. Participant who was not currently vaccinated against Neisseria meningitidis, unless the participant agrees to receive prophylactic treatment with appropriate antibiotics for at least 8 months after the last infusion of study drug or until at least 2 weeks after the participant receives vaccination against Neisseria meningitidis.