Chamblee

Researchers are evaluating the use of baloxavir marboxil in children under 12 years old with influenza. This study has two parts: Part A focuses on checking for resistance-related changes in the virus before and after treatment, while Part B looks at how influenza might spread from young children treated with baloxavir marboxil to their household contacts. Enrollment for Part B has stopped as per the latest protocol. Baloxavir marboxil is given as an oral suspension, with the dose based on the child's body weight: 80 mg for those 80 kg or more, 40 mg for 20 to less than 80 kg, and 2 mg per kg for those under 20 kg. Part A involves monitoring these children for resistance changes at baseline and during treatment on specific days. Part B included participants from Part A who lived with household contacts, assessing transmission, but no new participants are being enrolled in this part. Participants will be involved in screening to confirm influenza and absence of COVID-19, with symptom onset within 48 hours before starting treatment. Researchers will measure resistance-associated viral changes at baseline and during treatment days 4, 6, and 10. Household contacts in Part B were also assessed for influenza transmission risk and monitored through scheduled visits, but Part B enrollment is closed. The total study duration varies depending on participation in Parts A and B.