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IRIS: Oseltamivir resistance highest after pandemic
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SAN DIEGO — Emergent resistance to oseltamivir in patients with influenza A virus was commonly observed in children aged 1 to 5 years; no effect on symptom resolution was observed and there was a modest effect on viral clearance, according to 3-year data from the Influenza Resistance Information Study presented here.
“The resistance rate was highest during the post-pandemic season as compared with the pandemic season,” Martin Schutten, PhD, of the virology department at Erasmus Medical Center in Rotterdam, Netherlands, said during a presentation.
Martin Schutten
The Influenza Resistance Information Study (IRIS) was created in 2008 to assess neuraminidase inhibitor (NAI) resistance and the clinical course of influenza in children aged 1 to 12 years and in those aged at least 13 years who were treated and untreated with neuraminidase inhibitors.
For the global observational trial, Schutten and colleagues collected throat and nasal swabs from patients with influenza-like illness and/or a positive rapid test result for influenza. Swabs were collected on days 1, 3, 6 and 10. Three-year data were presented.
Of the 1,799 samples that tested positive with a single influenza strain, 1,234 patients had influenza A. Of these, 759 were administered oseltamivir monotherapy (Tamiflu, Roche). After day 1, emergent resistance was detected in 19 patients with influenza A who received oseltamivir. Twenty-six percent of these patients tested positive for Influenza A RNA at day 10, despite their symptoms being resolved by day 6.
Resistance was mainly observed in influenza A 2009pdmH1N1 and very low in influenza A H3N2 and influenza B, according to Schutten.
One patient experienced moderate or minor symptoms up to day 14 and had persistently poor appetite, despite testing negative on day 10.
“Despite the fact that the clinical impact of oseltamivir resistance is low at the moment, vigilance and continuous monitoring of resistance rates in post-marketing clinical trials is recommended especially in a population vulnerable to development of serious disease after influenza infection,” he told Infectious Disease News. “Spread of resistant strains to more vulnerable patients may be of concern and proper hygienic measures around treated and untreated patients therefore remains needed.”
For more information:
Schutten M. #32. Presented at: ID Week. Oct. 17-21, 2012; San Diego.
Disclosure: Schutten reports being a research contractor and scientific adviser for F. Hoffmann-La Roche and receiving consulting fees and research grants from the company.