Influenza viruses are classified into 4 types: A, B, C, and thogotovirus. Influenza A viruses are the most common of these four classifications and have the largest host range.1,2 Some researchers suggest that appropriate therapy helps shorten the duration of illness and decrease the incidence of influenza mortality.1,2 A Cochrane review was released recently, in the midst of flu season, which discussed the role of neuraminidase inhibitors in the management of influenza in healthy adults and children.
The reviewers included and analyzed data from 25 studies (15 oseltamivir and 10 zanamivir studies). The majority of the participants were adults during influenza season in both hemispheres. Intention-to-treat (ITT) population consisted of people with influenza-like illness symptoms. Time to first alleviation of symptoms in ITT- population was a median of 160 hours (range 125 to 192 hours) in the placebo groups and oseltamivir shortened this by 21 hours (95% confidence interval [CI] -29.5 to -12.9 hours, P < 0.001; five studies), but there was no evidence of effect on hospitalizations (based on seven studies) with a median placebo group event rate of 0.84% (range 0% to 11%): odds ratio (OR) 0.95; 95% CI 0.57 to 1.61, P = 0.86.
These results are based on the comprehensive ITT population data. A post-protocol analysis showed that participants randomized to oseltamivir in treatment trials had reduced odds of being diagnosed with influenza (OR 0.83; 95% CI 0.73 to 0.94, P = 0.003; eight studies), probably due to an altered antibody response.
Zanamivir trials showed no evidence of this. However, analysis of zanamivir evidence was postponed because of a lack of clinical study reports. The authors concluded that there was a high risk of publication and reporting biases in the trial program of oseltamivir.
Therefore, it is difficult to draw conclusions about its effect on complications or transmission until more data about study protocol, reporting analysis plan, statistical analysis plan, and individual patient data are available from the drug manufacturer.
Ironically, a previous Cochrane review3 examining the efficacy of neuraminidase inhibitors in 1500 children diagnosed with influenza from three randomized clinical trials reported that neuraminidase inhibitors may actually have a role in reducing influenza symptoms in healthy children with influenza A but not at-risk patients, which really does not make any sense since the priority is for sick patients. Whether to give or not give neuraminidase to adults is a question that has yet to be answered. Perhaps Roche needs to prepare their supporting documentation before winter.
1. Souza, MJ. Influenza. Journal of Exotic Pet Medicine 2011;20(1):4–8
2. Jefferson T, et al. Neuraminidase inhibitors for preventing and treating influenza in healthy adults and children. Cochrane Database of Systematic Reviews
2012;1:CD008965. doi: 10.1002/14651858.CD008965.pub3.
3. Matheson NJ, Symmonds-Abrahams M, Sheikh A, et al. Neuraminidase inhibitors for preventing and treating influenza in children. Cochrane Database of Systematic Reviews
2006;(1):CD002744. doi: 10.1002/14651858.CD002744.