For more information regarding Bristol-Myers Squibb Clinical Trial participation, please visit www.BMSStudyConnect.com Inclusion Criteria: - A confirmed virological diagnosis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection (by reverse-transcription polymerase chain reaction (RT-PCR)). - Hospitalized (or in the Emergency Department awaiting a bed after hospitalization) - Respiratory compromise as defined by requirement of oxygen supplementation to maintain oxygen saturation ≥ 93% but not requiring mechanical ventilation - Abnormal chest X-ray consistent with COVID-19 and not indicating other serious medical condition that would serve as an exclusionary criteria - Women and men must agree to follow specific methods of contraception, if applicable Exclusion Criteria: - Women who are breastfeeding - Recent acute infection defined as: i) Any acute infection within 60 days prior to randomization that required hospitalization or treatment with parenteral antibiotics (not COVID-19 related) ii) Any acute infection within 30 days prior to randomization that required oral antimicrobial or antiviral therapy - History of chronic or recurrent bacterial infection (e.g., chronic pyelonephritis, osteomyelitis, bronchiectasis) - Prior exposure to BMS-188667 (abatacept) Other protocol-defined inclusion/exclusion criteria apply