Cost-Effectiveness of Ensitrelvir for COVID-19 Post-Exposure Prophylaxis Among High-Risk Household Contacts in Japan: A Model-Based Cost-Utility Analysis
- 1Chiba University Hospital
Abstract
BackgroundEnsitrelvir reduced symptomatic COVID-19 after household exposure in the SCORPIO-PEP trial, but its economic value as post-exposure prophylaxis is unknown.
ObjectiveTo estimate the cost-effectiveness of ensitrelvir post-exposure prophylaxis for high-risk household contacts in Japan.
MethodsWe developed a decision-analytic cost-utility model from the Japanese public healthcare payer perspective. Trial risks of symptomatic COVID-19 through day 10 were linked to Japanese evidence on hospitalization, mortality, costs, quality of life, and life expectancy. Because the trial observed no COVID-19-related hospitalization or death, downstream outcomes were modeled only through prevention of symptomatic disease. We performed deterministic, probabilistic, structural, subgroup, and threshold analyses.
ResultsEnsitrelvir increased costs by JPY 54,945 and gained 0.003267 QALYs per exposed contact, yielding an ICER of JPY 16.82 million/QALY. None of 10,000 simulations was cost-effective at JPY 5 million/QALY. Applying the overall-trial relative risk to the high-risk baseline yielded JPY 19.24 million/QALY. Restricting post-acute utility loss to 6 months, halving it, or excluding it yielded ICERs of JPY 23.62 million, JPY 26.76 million, and JPY 65.51 million/QALY, respectively. The drug acquisition-cost threshold was JPY 11,021 per course.
ConclusionsAt current Japanese costs, ensitrelvir post-exposure prophylaxis for high-risk household contacts was unlikely to be cost-effective at JPY 5 million/QALY. This conclusion remained unfavorable under conservative efficacy, post-acute utility, hospitalization-attribution, and mortality assumptions. Severe-outcome benefits remain model-based extrapolations rather than trial-observed effects.
Key Points for Decision MakersO_LIThe pivotal post-exposure prophylaxis trial showed a substantial reduction in symptomatic COVID-19, but no COVID-19-related hospitalization or death occurred; modeled severe-outcome benefits therefore depend on external Japanese evidence. C_LIO_LIAt current Japanese drug and delivery costs, the base-case ICER was JPY 16.82 million per QALY. The probability of cost-effectiveness was 0% at JPY 5 million per QALY and 2.28% at JPY 10 million per QALY. C_LIO_LIThe acquisition-cost threshold was approximately JPY 11,000 per course. Conservative efficacy and post-acute utility scenarios remained above JPY 19 million and JPY 23 million per QALY, respectively. C_LI
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BibTeX
@misc{taniguchi2026costeffectiveness,
title = {{Cost-Effectiveness of Ensitrelvir for COVID-19 Post-Exposure Prophylaxis Among High-Risk Household Contacts in Japan: A Model-Based Cost-Utility Analysis}},
author = {T. Taniguchi and M. Yahaba and H. Yoshikawa and H. Igari and D. Sato},
howpublished = {medRxiv},
year = {2026},
month = sep,
doi = {10.64898/2026.09.15.26361876},
url = {https://www.medrxiv.org/content/10.64898/2026.09.15.26361876v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Cost-Effectiveness of Ensitrelvir for COVID-19 Post-Exposure Prophylaxis Among High-Risk Household Contacts in Japan: A Model-Based Cost-Utility Analysis
AU - T. Taniguchi
AU - M. Yahaba
AU - H. Yoshikawa
AU - H. Igari
AU - D. Sato
PY - 2026
DA - 2026/09/15
PB - medRxiv
DO - 10.64898/2026.09.15.26361876
UR - https://www.medrxiv.org/content/10.64898/2026.09.15.26361876v1
AB - BackgroundEnsitrelvir reduced symptomatic COVID-19 after household exposure in the SCORPIO-PEP trial, but its economic value as post-exposure prophylaxis is unknown. ObjectiveTo estimate the cost-effectiveness of ensitrelvir post-exposure prophylaxis for high-risk household contacts in Japan. MethodsWe developed a decision-analytic cost-utility model from the Japanese public healthcare payer perspective. Trial risks of symptomatic COVID-19 through day 10 were linked to Japanese evidence on hospitalization, mortality, costs, quality of life, and life expectancy. Because the trial observed no COVID-19-related hospitalization or death, downstream outcomes were modeled only through prevention of symptomatic disease. We performed deterministic, probabilistic, structural, subgroup, and threshold analyses. ResultsEnsitrelvir increased costs by JPY 54,945 and gained 0.003267 QALYs per exposed contact, yielding an ICER of JPY 16.82 million/QALY. None of 10,000 simulations was cost-effective at JPY 5 million/QALY. Applying the overall-trial relative risk to the high-risk baseline yielded JPY 19.24 million/QALY. Restricting post-acute utility loss to 6 months, halving it, or excluding it yielded ICERs of JPY 23.62 million, JPY 26.76 million, and JPY 65.51 million/QALY, respectively. The drug acquisition-cost threshold was JPY 11,021 per course. ConclusionsAt current Japanese costs, ensitrelvir post-exposure prophylaxis for high-risk household contacts was unlikely to be cost-effective at JPY 5 million/QALY. This conclusion remained unfavorable under conservative efficacy, post-acute utility, hospitalization-attribution, and mortality assumptions. Severe-outcome benefits remain model-based extrapolations rather than trial-observed effects. Key Points for Decision MakersO_LIThe pivotal post-exposure prophylaxis trial showed a substantial reduction in symptomatic COVID-19, but no COVID-19-related hospitalization or death occurred; modeled severe-outcome benefits therefore depend on external Japanese evidence. C_LIO_LIAt current Japanese drug and delivery costs, the base-case ICER was JPY 16.82 million per QALY. The probability of cost-effectiveness was 0% at JPY 5 million per QALY and 2.28% at JPY 10 million per QALY. C_LIO_LIThe acquisition-cost threshold was approximately JPY 11,000 per course. Conservative efficacy and post-acute utility scenarios remained above JPY 19 million and JPY 23 million per QALY, respectively. C_LI
ER -