Virus susceptibility and clinical effectiveness of anti-influenza drugs during the 2010–2011 influenza season in Russia

•Influenza viruses from the 2010–2011 epidemic season were found to be susceptible to oseltamivir and umifenovir.•Umifenovir was found to be effective against oseltamivir-resistant influenza viruses in cell culture-based assays.•Oseltamivir and umifenovir were found to be effective against infection caused by the pandemic A(H1N1)pdm09 virus in mice.•Oseltamivir and umifenovir treatment decreased the duration of symptoms in hospitalized influenza-infected patients.

SummaryBackgroundAntiviral drugs are critical adjuncts to influenza vaccination. This study determined the in vitro susceptibilities of influenza A and B viruses isolated in the 2010–2011 season in Russia to the neuraminidase inhibitor oseltamivir and the hemagglutinin fusion inhibitor umifenovir and clinical efficacy of this antiviral drugs in this season.MethodsThe antiviral potency of these drugs against A(H1N1)pdm09 virus in mice was assessed. Importantly, the clinical effectiveness of oseltamivir and umifenovir was evaluated in a retrospective study conducted in 26 regions of Russia.ResultsAll tested viruses (n = 36) were susceptible to oseltamivir and umifenovir in vitro. Oseltamivir (10 mg/kg/day) and umifenovir (60 mg/kg/day) significantly increased the survival of mice challenged with A/California/04/2009 (H1N1)pdm09 virus (p < 0.05). Influenza infection was laboratory-confirmed in 442 patients among 1462 patients hospitalized with acute respiratory infections. The treatment of influenza-infected patients within 48 h of symptom onset with oseltamivir and umifenovir was associated with a significant decrease in the duration of illness (2–3 days) and symptoms (p < 0.001). Pneumonia was observed in none of the patients treated with oseltamivir and in 0.3% of the patients treated with umifenovir, compared to 23.7% of patients who did not receive antiviral therapy (p < 0.001).ConclusionsThis study provided experimental and clinical evidence of the efficacy of oseltamivir and umifenovir against influenza viruses, representatives of which have continued to circulate in post-pandemic seasons.