OBJECTIVETo evaluate the efficacy and safety of oseltamivir phosphate as treatment for naturally acquired influenza infection.

METHODSThis study was conducted as a double-blind, randomized, placebo-controlled, multicenter trial during the influenza epidemic season from January to April 2001 at 7 centers in China. A total of 478 adults without other medical history, aged 18 to 65 years, were enrolled into the study. All subjects demonstrated febrile respiratory illness of no more than 36 hours' duration with a temperature of 37.8 degrees C or more plus at least two of the following symptoms: coryza/nasal congestion, sore throat, cough, myalgia/muscles aches and pain, fatigue, headache or chills/sweats. Individuals were randomized into either the oseltamivir phosphate or placebo group with identical-looking capsules. Either oral oseltamivir phosphate, 75 mg twice daily, or placebo was administered to the subjects for 5 days.

RESULTSA total of 451 individuals were analyzed for efficacy as the intent-to-treat population (ITT) (216 oseltamivir and 235 placebo) and 273 individuals were identified as influenza-infected through laboratory test, who were then defined as the intent-to-treat infected population (ITTI) (134 oseltamivir and 139 placebo). Four hundred and fifty nine individuals were included in the safety analysis. In the ITTI population, the cumulative alleviation proportion of oseltamivir group was significantly higher than that of the placebo group (P = 0.0466)). The median duration of illness was 91.6 h [95% confidence interval (CI) = 80.2 - 101.3 h] in the oseltamivir group and 95 h (95% CI = 84.5 - 105.3 h) in the placebo group. The median area under the curve of decreased total score was significantly higher in the oseltamivir group than in the placebo group, 1382.9 and 1236.7 score-hours, respectively (P = 0.0196). For the ITT population, similar results were observed. Adverse events (AE) were similarly reported in both the oseltamivir group and the placebo group. The main adverse events following test drug were gastrointestinal symptoms, neurological symptoms and rashes.

CONCLUSIONOseltamivir was effective and well tolerated as treatment of early naturally acquired influenza.