The FDA recently approved the use of baloxavir marboxil (baloxavir) in patients aged 12–64 years with uncomplicated influenza [1]. The effectiveness of baloxavir had been tested in one phase III trial named CAPSTONE-1 [2]. It consisted of two subtrials: one subtrial compared baloxavir (40 mg once) with placebo and oseltamivir in adult patients, and the other baloxavir with placebo in adolescent patients (total n = 1436). The trial was performed in Japan, the United States, and Canada. In the reported primary efficacy analysis, baloxavir reduced the time to alleviation of flu symptoms with 26.5 hours compared to placebo.