Association of baloxavir marboxil prescription with subsequent medical resource utilization among school‐aged children with influenza

Baloxavir marboxil is a novel antiviral agent for influenza, introduced into clinical practice in 2018. A concern remains about the variant virus with reduced susceptibility after baloxavir exposure and its clinical consequences such as healthcare-seeking behavior.Using a healthcare database in Japan, we compared the medical resource use following baloxavir and neuraminidase inhibitors (NAIs) treatment among children aged 7-15 years. The study period was from December 2018 to March 2019. The primary endpoint was the composite of hospitalization, laboratory and radiological tests, and antibiotic use over 1-9 days of antiviral treatment. As exploratory analyses, secondary outcomes being each single component of the primary composite were assessed and subgroup analyses comparing baloxavir with each NAI were done.Data from 115 867 prescriptions in 115 238 children were analyzed (median age: 10 years; severe influenza risk in 26%; baloxavir accounting for 43%). Overall, baloxavir use did not increase subsequent medical resource utilization in the composite endpoint (adjusted odds ratio [aOR]: 1.04; 95% confidence interval [CI]: 0.99-1.09; P = 0.14), as were likelihoods of other secondary outcomes. In the subgroup analysis, baloxavir use was associated with higher medical resource use than oseltamivir (aOR: 1.21; 95% CI: 1.13-1.31; P < 0.001) and lower resource use than zanamivir (aOR: 0.93; 95% CI 0.86-1.00; P = 0.040).Based on a single-year experience in Japan, prescribing baloxavir rather than NAIs did not increase medical resource utilization within 9 days of treatment, except in one exploratory comparison with oseltamivir.