Efficacy of baloxavir marboxil as a prophylactic against influenza among in-patients and analysis of influenza virus mutations in their isolates at a Japanese hospital during the 2023–2024 flu season

• DOI: 10.1186/s40780-025-00418-5
• Publication Date: 2025-03-17T11:41:12Z
• Authors: Akihide Fujii; Tomohiro Oishi; Eisei Kondo; Zyunko Morihara; Yuka Ikeda; Hideyuki Sumida; Youko Ninomiya; Satoe Uesugi; Kimie Okazaki; Daisuke Yoshioka; Miyoko Kobayashi; Hideho Wada

Abstract Background Baloxavir marboxil (baloxavir) is a new anti-influenza drug that works as cap-dependent endonuclease inhibitor. It approved for prophylactic use against influenza in Japan, but there are few reports on this usage hospitalized in-patients. reportedly reduces patient susceptibility to through mechanism involving amino acid substitution. Methods Between August 2023 and July 2024, we investigated the efficacy of baloxavir among in-patients at our hospital who had close contact with patients were infected viruses same rooms. We also I38T virus variant samples taken from hospital. Results enrolled total 45 other confirmed be room. Among 34 them prescribed prophylactically, none developed within 5 days their last patients. Conversely, 11 did not baloxavir, three became following ( P = 0.012). In 85 influenza, 25 H1N1 types 60 H3N2. detected endonuclease-baloxavir complex structure two H3N2-type samples. Both these contracted children. Conclusions According results, represents an effective However, genetic mutations related decreased such variant, should nevertheless exercise higher levels caution—particularly around