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Background Duration of viral shedding is a determinant of infectivity and transmissibility, but few data exist about oseltamivir's ability to alter viral shedding. Methods From January 2012 through October 2017, a randomized, double-blinded multicenter clinical trial was conducted in adults aged 18–64 years at 42 sites in Thailand, the United States, and Argentina. Participants with influenza A or B and without risk factors for complications of influenza were screened for the study. Eligible participants were randomized to receive oseltamivir 75 mg or placebo twice daily for 5 days. The primary endpoint was the percentage of participants with virus detectable by polymerase chain reaction in nasopharyngeal swab at day 3. Results Of 716 adults screened for the study, 558 were randomized, and 501 were confirmed to have influenza. Forty-six participants in the pilot study were excluded, and 449 of the 455 participants in the population for the primary analysis had day 3 viral shedding results. Ninety-nine (45.0%) of 220 participants in the oseltamivir arm had virus detected at day 3 compared with 131 (57.2%) of 229 participants in the placebo arm (absolute difference of −12.2% [−21.4%, −3.0%], P =;.010). The median time to alleviation of symptoms was 79.0 hours for the oseltamivir arm and 84.0 hours for the placebo arm (P =;.34) in those with confirmed influenza infection. Conclusions Oseltamivir decreased viral shedding in this low-risk population. However, in the population enrolled in this study, it did not significantly decrease the time to resolution of clinical symptoms. Clinical Trials Registration NCT01314911. [ABSTRACT FROM AUTHOR]