What is it about?
Did favipiravir really reduce mortality from a viral haemorrhagic fever by 10%? Japan approved this antiviral, originally stockpiled for pandemic influenza, for treating SFTS in 2024 based on a single-arm trial reporting 17% mortality. But real-world data without favipiravir also showed 17–18%, prompting us to re-examine the evidence.
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Photo by Giuseppe CUZZOCREA on Unsplash
Why is it important?
SFTS is a rare but life-threatening viral infection. When treatment effects are overstated, it can lead to inappropriate clinical practices or premature policy decisions. Given that favipiravir’s approval may influence future regulatory pathways, it is important to critically assess the robustness and interpretation of the supporting evidence.
Perspectives
We took a closer look at the original trial and compared it with national registry data. By analysing differences in patient populations and context, we propose using real-world data as external controls to re-evaluate the true effectiveness of favipiravir. This approach may guide future research and help improve standards for drug evaluation in emerging infections.
Kenji Kubo
Read the Original
This page is a summary of: Re-evaluating a single-arm trial of favipiravir for severe fever with thrombocytopenia syndrome in Japan: A proposal to use real-world data as external controls, PLoS Neglected Tropical Diseases, August 2025, PLOS,
DOI: 10.1371/journal.pntd.0013279.
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