Clinical effectiveness of neuraminidase inhibitors-oseltamivir, zanamivir, laninamivir, and peramivir-for treatment of influenza A(H3N2) and A(H1N1)pdm09 infection: an observational study in the 2010-2011 influenza season in Japan

The clinical effectiveness of the newly released neuraminidase inhibitors (NAIs) laninamivir and peramivir has not been sufficiently evaluated in influenza-infected patients in clinical and practical settings. In this study, we analyzed the clinical data of 211 patients infected with influenza A virus subtype H3N2 (A(H3N2)) and 45 patients infected with influenza A virus subtype H1N1pdm (A(H1N1)pdm09) who received the NAIs oseltamivir, zanamivir, laninamivir, or peramivir during the 2010-2011 influenza season. The duration of fever from the first dose of the NAI to fever alleviation to <37.5 °C was evaluated as an indicator of the clinical effectiveness of the NAIs in the influenza-infected patients. For the A(H3N2)-infected patients, Kaplan-Meier analysis showed the peramivir treatment group had the fastest time of fever alleviation to <37.5 °C (median 17.0 h, 95 % confidence interval [CI] 7.2-26.8 h) of the four treatment groups. No significant difference was found in the time to fever alleviation among the other antivirals, oseltamivir, zanamivir, and laninamivir. Results of multivariate analysis, using a Cox proportional-hazards model (hazard ratio 3.321) adjusted for the factors age, sex, body weight, vaccination status, time from onset to the clinic visit, and body temperature showed significantly faster fever alleviation in the peramivir treatment group compared with the oseltamivir treatment group. For the A(H1N1)pdm09-infected patients, only the oseltamivir and zanamivir treatment groups were compared, and no significant difference in time to alleviation of fever was observed between the two groups. Based on a cycling probe real-time polymerase chain reaction (PCR) assay, none of the A(H1N1)pdm09 strains in this study had the H275Y mutation conferring oseltamivir resistance. Further evaluation of the clinical effectiveness of the newly released NAIs for influenza-infected patients, including those infected with A(H1N1)pdm09, is needed.