Study to Assess the Safety, Pharmacokinetics, and Efficacy of Baloxavir Marboxil in Healthy Pediatric Participants From Birth to < 1 Year With Influenza-Like Symptoms

Exclusion Criteria

• •Hospitalized for complications of influenza or significant comorbidities
• •Concurrent infections requiring systemic antiviral therapy at screening
• •Require, in the opinion of the investigator, any of the prohibited medication during the study
• •Preterm neonates (born at \< 37 weeks gestation) and/or weighing \< 2.5 kg at screening
• •Previous treatment with peramivir, laninamivir, oseltamivir, zanamivir, or amantadine within 2 weeks prior to screening
• •Immunization with a live/attenuated influenza vaccine during the 2 weeks prior to screening
• •Concomitant treatment with steroids or other immuno-suppressant therapy
• •Known HIV infection or other immunosuppressive disorder
• •Uncontrolled renal, vascular, neurologic or metabolic disease (e.g., diabetes, thyroid disorders, adrenal disease), hepatitis, cirrhosis, or pulmonary disease or participants with known chronic renal failure
• •Active cancer at any site
• •History of organ transplant
• •Known hypersensitivity to study drug (i.e., baloxavir marboxil) or to acetaminophen
• •Participation in a clinical trial within 4 weeks or five half-lives of exposure to an investigational drug prior to screening, whichever is longer