Suraxavir Marboxil And Oseltamivir for Influenza Prophylaxis Under a Hospital-based Setting

1.Inclusion Criteria: (1)Inclusion Criteria for Index Cases: ① Patients hospitalized at a participating medical institution. * The subject and/or their legal guardian agrees to participate in this clinical study, has signed the informed consent form, and is able to comply with the protocol requirements for follow-up and complete all study procedures and assessments. * Age ≥ 2 years. * Positive for influenza virus as determined by a Rapid Antigen Test (RAT) or Nucleic Acid Amplification Test (NAAT) on a respiratory specimen (e.g., oropharyngeal swab, nasopharyngeal swab, sputum, or bronchoalveolar lavage fluid). (2) Inclusion Criteria for Room Contacts: ① Patients hospitalized at a participating medical institution. * The subject and/or their legal guardian agrees to participate in this clinical study, has signed the informed consent form, and is able to comply with the protocol requirements for follow-up and complete all study procedures and assessments. ③ Age ≥ 12 years. * Expected to remain hospitalized for ≥ 72 hours. * Shares a room with at least one hospitalized index case who has been confirmed with influenza virus infection by RAT or NAAT on a respiratory specimen within the last 120 hours and developed influenza-related symptoms within the last 120 hours, and is expected to share the same room for ≥ 24 hours. ⑥ Negative for influenza virus as determined by a Nucleic Acid Amplification Test (NAAT) on a throat swab collected on Day 1. 3.Exclusion Criteria (1) Index Cases There are no exclusion criteria for index cases. (2) Exclusion Criteria for Room Contacts: * Room contacts with a known allergy to the active ingredients or excipients of the investigational drugs. * Room contacts who have been diagnosed with or have had an influenza virus infection in the past 12 weeks. * Use of any anti-influenza antiviral drugs within 2 weeks prior to screening, including: neuraminidase inhibitors, polymerase inhibitors, hemagglutinin inhibitors, and M2 ion channel blockers (e.g., Oseltamivir, Zanamivir, Peramivir, Favipiravir, Arbidol, Baloxavir Marboxil, Amantadine, or Rimantadine, or other anti-influenza drugs approved by the NMPA). * Known to be pregnant or breastfeeding. (Subjects who suspect they may be pregnant must report this to the investigator, who will confirm with a pregnancy test). * History of fever (axillary temperature ≥ 37.3°C) within 72 hours prior to screening. * Child-Pugh class B or C, or an eGFR ≤ 60 mL·min-¹·(1.73 m²)-¹. ⑦ Any subject deemed unsuitable for participation in the study by the investigator.