(P-073) Baloxavir Marboxil vs Neuraminidase Inhibitors Prescription on Subsequent Medical Resource Utilization Among School-aged Children with Influenza: Analysis of Two Consecutive Seasons in Japan

Background: Baloxavir marboxil is a new class of anti-influenza drug, and there remains a concern for appearance of less-susceptible variant virus to this drug class. We previously reported the first-year experience of baloxavir utilization for children with influenza in Japan, with emphasis on the subsequent medical resource use as compared with neuraminidase inhibitors (NAIs).

Objectives: To update the information by analyzing data of two consecutive seasons.

Methods: We used healthcare database which was comprised of 200 insurance plans in Japan. Children aged 7-15 years who were prescribed either baloxavir or NAIs during the influenza season of 2018/19 and 2019/2020 were eligible. The composite of hospitalization, laboratory and radiological tests, and antibiotic use within 1-9 days of antiviral treatment was the primary outcome of interest. We hypothesized that this outcome would work as a proxy of consequence of variant virus. Multivariate, mixed-effect logistic regression was used to adjust patient characteristics, along with correlations within seasons and those within children with repeated influenza infections. We also conducted a multiplicity-adjusted subgroup analyses comparing children exposed to baloxavir and those exposed to each NAI: oseltamivir, zanamivir and laninamivir.

Results: A total of 261 899 cases were included, being baloxavir prescription accounted for 42.9% (60 233/140 363) and 9.1% (10 009/121 536) in 2018/2019 and 2019/2020 season, respectively. The primary endpoint occurred in 7.9% (20 790/261 899), and this risk did not differ between the recipients of baloxavir and NAIs both in the primary analysis (adjusted odds ratio: 1.08 [reference: baloxavir]; 95% confidence interval: 0.97-1.20; P = 0.16) and in subgroup analyses.

Conclusions: The proportion of baloxavir prescription has declined dramatically in the second season. The post-exposure resource utilization between baloxavir recipients and NAIs recipients did not differ in the two consecutive seasons of real-world experience among Japanese children.