Baloxavir post-exposure prophylaxis linked to larger estimated reduction in household influenza

A systematic review found that baloxavir marboxil given to exposed household contacts was associated with larger estimated reductions in household influenza than treatment of infected index patients. The review included four studies involving 5,784 participants: 1,991 index patients and 3,793 household contacts. Three studies were conducted in Japan, and one was the 15-country multinational CENTERSTONE trial.

Across the available studies, post-exposure prophylaxis, or PEP, was associated with relative risk reductions of 57–86% in household influenza outcomes compared with control regimens, while index-patient treatment was associated with more modest relative risk reductions of 24–29%. The review examined two distinct ways in which baloxavir could be used to limit influenza transmission within households. In the index-patient strategy, an infected person receives baloxavir with the aim of reducing infectiousness and onward transmission to household contacts.

In the PEP strategy, contacts already exposed to the index patient receive the antiviral to prevent infection from becoming established. The studies assessed laboratory-confirmed or symptomatic influenza among contacts, using comparisons that included placebo or neuraminidase inhibitors. The investigators searched PubMed, Embase, Web of Science and the Cochrane Library for randomized and observational studies published or indexed from 1 January 2018 through 25 June 2025.

The largest estimated effects were reported for PEP. Across the included evidence, giving baloxavir to exposed household contacts was associated with relative risk reductions ranging from 57% to 86% in household influenza outcomes. These results support a larger estimated protective association for PEP than for treating infected household members alone.

Evidence for index-patient treatment was less pronounced. Baloxavir treatment of infected individuals was associated with relative risk reductions of 24–29% in household transmission outcomes, indicating a smaller estimated indirect effect than the range reported for PEP. One outcome—a 24% reduction in symptomatic transmission measured five days after treatment—did not reach statistical significance, with P = 0.16.

The review therefore described baloxavir-based strategies as potentially useful for reducing household influenza transmission while distinguishing the more modest and, in that five-day result, statistically uncertain findings for index-patient treatment.

Subject of Research: Baloxavir-based strategies for reducing influenza transmission within households

Article Title: Effectiveness of baloxavir marboxil in reducing household influenza transmission: a systematic review

Article References: Niu, B., Wu, G., Chen, R., Zhang, W., Yuan, Z., Bai, Y., & Du, Z. (2026). Effectiveness of baloxavir marboxil in reducing household influenza transmission: a systematic review. BMC Infectious Diseases. https://doi.org/10.1186/s12879-026-14294-3

Image Credits: AI Generated

DOI: 10.1186/s12879-026-14294-3

Keywords: baloxavir marboxil, influenza, household transmission, post-exposure prophylaxis, index-patient treatment, antiviral, systematic review, CENTERSTONE trial, Japan, Effectiveness, baloxavir, marboxil