Comparison of Household Transmission of Influenza Virus From Index Patients Treated With Baloxavir Marboxil or Neuraminidase Inhibitors: A Health Insurance Claims Database Study.

BACKGROUND Baloxavir marboxil (baloxavir), an anti-influenza drug with a novel mechanism of action, is expected to reduce influenza transmission by rapid reduction of viral load. The incidence of household transmission was compared between index patients (IPs) treated with baloxavir and those with neuraminidase inhibitors. METHODS Using a Japanese claims database provided by JMDC Inc., the first family members with influenza diagnosis during 2018/2019 influenza season were identified as IPs, and the diagnosis date was designated Day 1. According to the anti-influenza drug dispensed to the IP, their families were classified into oral baloxavir group and three controls; oral oseltamivir group (a primary control), inhaled zanamivir group, and inhaled laninamivir group. A household transmission was defined as influenza diagnosed for any non-IP family members during Days 3-8. The incidence of household transmission was compared between groups using a logistic regression model adjusting backgrounds of IPs. RESULTS The proportion of families with household transmission was 17.98% (15,226/84,672) in the baloxavir group and 24.16% (14,983/62,004) in the oseltamivir group. The covariate-adjusted odds ratio (oseltamivir/baloxavir) was 1.09 [95% confidence interval, 1.05-1.12], which indicated significantly lower incidence in the baloxavir group. Adjusted odds ratios (controls/baloxavir) against zanamivir and laninamivir were 0.93 [0.89-0.97] and 0.99 [0.96-1.02], respectively. CONCLUSIONS Baloxavir may contribute to reduce the incidence of household transmission compared with oseltamivir, which is widely used for oral influenza treatment. In comparison between baloxavir and inhalants, a similar reduction was not shown and it might be due to unmeasured confounding by administration route differences.