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Randomized Controlled Trial
. 2024 May;18(5):e13302.
doi: 10.1111/irv.13302.

Comparative Effectiveness of Baloxavir Marboxil and Oseltamivir Treatment in Reducing Household Transmission of Influenza: A Post Hoc Analysis of the BLOCKSTONE Trial

Hideyuki Ikematsu  1 , Takamichi Baba  2 , Masaya M Saito  3 , Masahiro Kinoshita  4 , Shogo Miyazawa  5 , Ayano Hata  5 , Saki Nakano  5 , Yoshitake Kitanishi  5 , Frederick G Hayden  6
Affiliations
Randomized Controlled Trial

Comparative Effectiveness of Baloxavir Marboxil and Oseltamivir Treatment in Reducing Household Transmission of Influenza: A Post Hoc Analysis of the BLOCKSTONE Trial

Hideyuki Ikematsu et al. Influenza Other Respir Viruses. 2024 May.

Abstract

Background: The transmission of influenza virus in households, especially by children, is a major route of infection. Prior studies suggest that timely antiviral treatment of ill cases may reduce infection in household contacts. The aim of the study was to compare the effects of oseltamivir (OTV) and baloxavir marboxil (BXM) treatment of index cases on the secondary attack rate (SAR) of influenza within household.

Methods: A post hoc analysis was done in BLOCKSTONE trial-a placebo-controlled, double-blinded post-exposure prophylaxis of BXM. Data were derived from the laboratory-confirmed index cases' household contacts who received placebo in the trial and also from household members who did not participate in the trial but completed illness questionnaires. To assess the SAR of household members, multivariate analyses adjusted for factors including age, vaccination status, and household size were performed and compared between contacts of index cases treated with BXM or OTV.

Results: In total, 185 index cases (116 treated with BXM and 69 treated with OTV) and 410 household contacts (201 from trial, 209 by questionnaire) were included. The Poisson regression modeling showed that the SAR in household contacts of index cases treated with BXM and OTV was 10.8% and 18.5%, respectively; the adjusted relative reduction in SAR was 41.8% (95% confidence interval: 1.0%-65.7%, p = 0.0456) greater with BXM than OTV. Similar reductions were found in contacts from the trial and those included by questionnaire.

Conclusion: BXM treatment of index cases appeared to result in a greater reduction in secondary household transmission than OTV treatment.

Keywords: Japan; baloxavir marboxil; household transmission; influenza treatment; oseltamivir.

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Conflict of interest statement

H.I. and M.S. report no conflicts of interest. T.B., M.K., S.M., A.H., S.N., and Y.K. are employees of and hold stocks in Shionogi & Co., Ltd. F.G.H. reports serving as a non‐compensated consultant and recipient of meeting travel support from F. Hoffmann‐La Roche and Shionogi and serving as a non‐compensated consultant for Arcturus, Asterivir, Cidara Therapeutics, Fujifilm Corporation, Genentech, Gilead Sciences, Janssen Pharmaceuticals, Merck, MediVector, Ridgeback, SAB Biotherapeutics, Sanofi‐Pasteur, Versatope, Via Nova Therapeutics, Eradivir and Vir Biotechnology.

Figures

FIGURE 1
FIGURE 1
Index case disposition. BXM, baloxavir marboxil; OTV, oseltamivir.
FIGURE 2
FIGURE 2
Secondary attack rate based on Poisson regression model. BXM, baloxavir marboxil; CI, confidence interval; OTV, oseltamivir; SAR, secondary attack rate. BXM was used as a reference against OTV to calculate the SAR rate. †Poisson regression model with the number of newly ill persons in the household as the outcome, treatment of the index case as the fixed effect, and household size, except for the index case, as offsets. ‡Poisson regression model with the number of newly ill persons in the household as the outcome, treatment of the index case as the fixed effect, age, influenza vaccination status within the previous 6 months of the index case and household size as covariates, and household size, except for the index case excluded, as offsets. In subgroup analysis by age and influenza subtype, age was excluded from the analysis model.
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