A Phase 2 Study to Investigate the Efficacy and Safety of Zelicapavir in Participants Aged ≥28 Days to ≤36 Months of Age Infected With Respiratory Syncytial Virus

Inclusion Criteria: * Participants diagnosed with RSV infection using an approved diagnostic assay, without known and/or documented coinfection with SARS-CoV-2 or influenza * Participant has signs of RSV infection with onset ≤3 days (72 hours) at the time of randomization * In the Investigator's opinion, the participant's caregiver understands and is able to comply with protocol requirements, instructions, and restrictions, and the participant is likely to complete the study as planned. The caregiver(s) should be of legal age. Exclusion Criteria: * Participant has any condition that in the opinion of the Investigator would interfere with the evaluation of the study drug or participant safety. * Participant has underlying immune deficiency. Participants with immunoglobulin A deficiency are not excluded. * Participant has had major surgery within 6 weeks prior to randomization or has major surgery planned during the course of the study. * Participant is currently taking either chronically or has taken within 7 days prior to randomization, or is anticipated to receive during the course of the study, systemic medications that are known to cause immunosuppression other than corticosteroids for \>5 days. * Participant has received an investigational agent within the last 30 days or 5 half-lives of the investigational agent, whichever is longer.