Hoffmann-La Roche
This study consists of two parts: Part A Surveillance and Part B Transmission. The main purpose of Part A is to evaluate the prevalence of pre-dose and treatment-emergent amino acid substitutions in pediatric participants' \<12 years with influenza treated with baloxavir marboxil. Part B will include a subset of Part A participants who have household contacts (HHCs) recruited to the study. Part B will evaluate the incidence of onward influenza transmission from pediatric index participants (IPs) under 5 years of age and those aged 5 to under 12 years, treated with baloxavir marboxil, to their HHCs. Participants will no longer be enrolled to Part B Transmission as per protocol version 3.
Inclusion Criteria (Part A): * Participants with symptoms suggestive of influenza based on investigator's judgement with diagnosis confirmed by a positive local influenza test within 24 hours before full study screening * Participants with a negative severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) test within 48 hours before full study screening * Time interval between onset of influenza symptoms and the start of pre-dose examinations at screening is 48 hours or less Inclusion Criteria (Part B): \[A\] IP: * Eligible to take part in Part A * Lives in a household with a HHC will…
Baloxavir marboxil will be administered as an oral suspension per body weight (≥80 kilograms \[kg\]: 80 milligrams \[mg\]; ≥20 kg to \< 80 kg: 40 mg; \<20 kg: 2 milligrams per kilogram \[mg/kg\]).