Study to Assess Adverse Events and How Intravenous (IV) ABBV-47D11 and IV ABBV-2B04 Given Alone and in Combination Moves Through the Body of Adult Participants With Coronavirus Disease 2019 (COVID-19)

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Lung failure is the main cause of death related to COVID-19 infection. The main objective of this study is to evaluate the safety and tolerability of ABBV-47D11 and ABBV-2B04 given alone and in combination to participants with COVID-19 infection. In addition, this study will evaluate the pharmacokinetics (how the body handles the study drug) and anti-viral activity of the study drug. ABBV-47D11 and ABBV-2B04 are investigational anti-SARS-CoV-2 monoclonal antibodies being developed for the treatment of COVID-19. Study will be conducted in two parts. In part A, participants will receive ABBV-47D11 or placebo. There is a 1 in 4 chance that participants will be assigned to placebo. In part B, participants will receive ABBV-2B04 alone or in combination with ABBV-47D11 or placebo. There is a 1 in 5 chance that participants will be assigned to placebo. Around 54 adult participants with COVID-19 will be enrolled in approximately 10 to 30 sites globally. In part A participants will receive single intravenous (into the veins) infusion of ABBV-47D11 or placebo on Day 1. In part B participants will receive single intravenous (into the veins) infusion of ABBV-2B04 alone or in combination with ABBV-47D11 or placebo on Day 1. Participants will be followed up for 106 days. There may be higher treatment burden for participants in this trial compared to their standard of care. The effect of the treatment will be checked by medical assessments, blood tests, nasal swabs and presence of side effects.