Study to Assess Efficacy and Safety of Baloxavir Marboxil In Combination With Standard-of-Care Neuraminidase Inhibitor In Hospitalized Participants With Severe Influenza

Inclusion Criteria

• •Adult participants: Signed informed consent by any participant capable of giving consent, or, where the participant is not capable of giving consent, by his or her legal/authorized representative
• •Adolescent participants not able to legally consent: written informed consent for study participation is obtained from participant's parents or legal guardian, with assent as appropriate by the participant, depending on the participant's level of understanding and capability to provide assent
• •Participants who require hospitalization for severe influenza or acquire influenza during hospitalization, the severity of which requires an extension of hospitalization
• •Diagnosis of influenza A and/or B by a positive Rapid Influenza Diagnostic Test (RIDT) or reverse transcriptase-polymerase chain reaction (RT-PCR)
• •The time interval between the onset of symptoms and randomization is within 96 hours
• •A score of ≥4 based on the National Early Warning Score 2 (NEWS2)
• •Participants will require objective criteria of seriousness defined by at least one of the following criteria:
• •Requires ventilation or supplemental oxygen to support respiration
• •Has a complication related to influenza that requires hospitalization (e.g., pneumonia, central nervous system involvement, myositis, rhabdomyolysis, acute exacerbation of chronic kidney disease, asthma or chronic obstructive pulmonary disease (COPD), severe dehydration, myocarditis, pericarditis, exacerbation of ischemic heart disease)
• •For women of childbearing potential: Agreement to remain abstinent or use contraceptive methods with a failure rate of \< 1% per year during the treatment period and for 28 days after the last dose of study treatment. Hormonal contraceptive methods must be supplemented by a barrier method.