Safety, clinical, and virologic assessments
fever, TTRF, throat, cough, influenza illness symptoms, nasal discharge/nasal congestion
VIRUS, RECURRENCE, RECURRENCE, ADVERSE EVENTS, CO-INFECTION, INFLUENZA
The incidence and severity of adverse events (AEs), vital signs, and clinical laboratory tests were assessed, and AEs were classified using the Medical Dictionary for Regulatory Activities Version 19.1. Clinical assessments including axillary temperature and severity of two influenza symptoms (cough and nasal discharge/nasal congestion) on a 4-point rating scale (0 = absent to 3 = severe) were recorded in an electronic diary. For virologic assessments, nasopharyngeal swabs (or throat swab if nasopharyngeal swab was not feasible) were collected by investigators (days 1, 2, 3 and/or 4, 6, and 9). Virus type/subtype and virus titer were determined. Co-infection was monitored using swab samples assayed by singleplex quantitative reverse transcription polymerase chain reaction (RT-PCR) for respiratory viruses (including influenza) and bacteria (Additional file Clinical endpoints included time to illness alleviation (TTIA), time to resolution of fever (TTRF), recurrence of influenza illness symptoms, and recurrence of fever. TTIA was defined as the time from baloxavir administration until the following criteria were met and sustained for ≥21.5 hours: cough and nasal discharge/nasal congestion both assessed as 0 (absent) or 1 (mild) and axillary temperature < 37.5 °C. TTRF was defined as an axillary temperature < 37.5 °C and sustained for ≥12 hours. Recurrence of symptoms was defined as a symptom score of moderate or severe at ≥1 time point after day 4 that was higher than the previous time point. Recurrence of fever was defined as resolution of fever before day 4 but then ≥37.5 °C body temperature after day 4, which was higher than the previous time point. Day 4 was used as the cut-off time based on the timing of transient increases in virus titer.Virologic endpoints were infectious virus titer (log