CDC responds in record time

CDC responds in record time Announcement Date: April 9, 2014

“CDC continues to recommend the use of the neuraminidase inhibitor antiviral drugs (oral oseltamivir and inhaled zanamivir) as an important adjunct to influenza vaccination in the treatment of influenza.”

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April 10, 2014 — CDC continues to recommend the use of the neuraminidase inhibitor antiviral drugs (oral oseltamivir and inhaled zanamivir) as an important adjunct to influenza vaccination in the treatment of influenza. CDC’s current influenza antiviral recommendations are available on the CDC website and are based on all available data, including the most recent Cochrane report, about the benefits of antiviral drugs in treating influenza.

CDC considers all of the published evidence available from Randomized Control Trials (RCT) conducted among outpatients and observational studies conducted among hospitalized patients, including benefits and risks from safety data, when issuing recommendations on antiviral treatment of influenza. These CDC recommendations emphasize early antiviral treatment as soon as possible for patients who are severely ill and for those who are at greatest risk for complications from influenza. This includes hospitalized patients with suspected or confirmed influenza, those with severe or progressive illness, and outpatients who are at high risk for influenza complications (for example, young children, people aged 65 years and older, pregnant women, and persons with certain underlying chronic medical conditions). In addition, because other reviews of RCTs and observational studies have found consistent clinical benefit of early oseltamivir treatment in reducing the risk of lower respiratory tract complications such as those requiring antibiotics, persons with uncomplicated influenza who are not in a high risk group and who present within 48 hours of illness onset can be treated with antiviral medications based upon clinical judgment.

One large study that was published recently, “Effectiveness of neuraminidase inhibitors in reducing mortality in patients admitted to hospital with influenza A(H1N1pdm09) virus infection: a meta-analysis of individual participant data”, adds to the growing body of evidence which supports that neuraminidase inhibitor treatment can reduce the risk of death in hospitalized patients with influenza.  In this meta-analysis of published studies, researchers compiled individual-level data from 78 observational studies across 38 countries on more than 29,000 patients who were hospitalized with 2009 H1N1 influenza virus infection during the 2009-10 pandemic. In this study among patients aged >16 years, treatment with a neuraminidase inhibitor antiviral drug was associated with a 25% reduction in the likelihood of death compared to no antiviral treatment. Early treatment with neuraminidase inhibitor antiviral drugs (i.e., within 48 hours of development of influenza illness) halved the risk of death compared to no antiviral treatment. This confirms findings from previous observational studies in hospitalized influenza patients that the clinical benefit of neuraminidase inhibitor antiviral treatment is greatest when started within two days of influenza illness onset.

A review of RCT data for the influenza neuraminidase inhibitor antiviral medications published by the Cochrane Collaboration updates a previous Cochrane review published in 2012, and raises questions about the value of antiviral medications for the prevention and treatment of influenza. The updated Cochrane review assessed full internal clinical study reports from manufacturers containing published and unpublished data from 46 randomized controlled trials (RCTs) of oral oseltamivir or inhaled zanamivir versus placebo for preventing and treating outpatients with mild illness who were otherwise healthy adults and children. The review concluded that in adults and children with influenza-like illness, early oral oseltamivir treatment shortens the duration of symptoms by approximately 17 hours and 29 hours, respectively, compared to placebo. This finding is similar to results in previously published RCTs which reported a reduction of approximately one day of laboratory-confirmed uncomplicated influenza illness in outpatients by early oral oseltamivir treatment versus placebo. One RCT in outpatients who were aged 1 to 3 years with uncomplicated influenza found a reduction of 3.5 days when oral oseltamivir treatment was started within 24 hours after illness onset. The Cochrane review concluded that inhaled zanamivir reduced symptoms in adults by approximately half a day compared to placebo, but had no significant effect in children. The Cochrane review reported no significant effect of oral oseltamivir treatment of outpatients on hospitalizations for adults or children, and the authors conclude that the treatment trials do not settle the question of whether the complications of influenza are reduced by treatment in outpatients because of a lack of diagnostic definitions.

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