Osaka, Japan—Which influenza antiviral is most effective at preventing intrafamilial transmission of influenza? A Japanese study used a simulation model to help answer that question.
Pointing out that influenza affects about a billion people globally every year, researchers compared baloxavir marboxil (BXM), a selective cap–dependent endonuclease inhibitor marketed as Xofluza in the United States, to oseltamivir (OTV), marketed as Tamiflu in terms of how effectively household flu spreads. Results were published in the journal Clinical Infectious Diseases.

Researchers used a Japanese claims database to identify index cases (ICs) as the first family member diagnosed with influenza during the 2018Ð2019 influenza season and classified the families into BXM or OTV groups based on the drug dispensed to that family member.

"Using a novel influenza intra-familial infection model, we simulated the duration of influenza infection in ICs based on agent-specific virus shedding periods," the authors explained. "Intra-familial infections were defined as non-IC family members infected during the agent-specific viral shedding period in ICs. The virus incubation periods in the non-IC family members were considered to exclude secondary infections from potentially external exposure. The primary endpoint was proportion of families with intra-familial infections. For between-group comparisons, we used a multivariate logistic regression model."

Results indicate that the median proportion of families with the intrafamilial transmission was 9.57% and 19.35% in the BXM (N = 84,672) and OTV (N = 62,004) groups, respectively. "The multivariate odds ratio of 1.73 (2.5th-97.5th percentiles, 1.68-1.77) indicated a substantially higher incidence of intra-familial infections in the OTV group versus the BXM group," the researchers point out. "Subgroup analyses by ICs' age category, virus type, and month of onset revealed similar trends favoring BXM."

In the U.S., the CDC recommends the following when it comes to antiviral use in influenza cases:

• For hospitalized patients with suspected or confirmed influenza, initiation of antiviral treatment with oral or enterically administered OTV is recommended as soon as possible.

• For outpatients with complications or progressive disease and suspected or confirmed influenza (e.g., pneumonia, or exacerbation of underlying chronic medical conditions), initiation of antiviral treatment with oral OTV is recommended as soon as possible.

• For outpatients with suspected or confirmed uncomplicated influenza, oral OTV, inhaled zanamivir, IV peramivir, or oral BXM may be used for treatment, depending on approved age groups and contraindications.

The CDC notes that in one randomized, controlled trial, BXM had greater efficacy than oseltamivir in adolescents and adults with influenza B virus infection.

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