Prophylactic efficacy of Relenza against influenza A and B

Trial description: In response to the European regulatory authorities, GSK is conducting a post-marketing observational study to assess the efficacy of Relenza when used as prophylaxis against influenza.SPECIFIC AIMS1. Determine the frequency of patients who received Relenza from October 2006 through April 2009, and among them the number who have no concurrent diagnosis of influenza, i.e., those receiving Relenza for prophylaxis, and among these the number who have a family member with a medical visit for influenza within three days preceding the above indentified patient's dispensing of Relenza. This is to determine the feasibility of conducting detailed analysis. 2. If analysis is feasible then tabulate the frequency of influenza-like-illness and respiratory outcomes in users of prophylactic Relenza and their family members and in family members of persons using Relenza for the treatment of influenza (i.e., index cases). 3. If analysis is feasible then estimate the direct effect of prophylactic Relenza on the occurrence of influenza-like-illness and respiratory outcomes, the secondary effect of Relenza treatment of influenza on susceptible family members, and the total effect of Relenza (treatment plus prophylaxis). METHODS Overview of Study Design This is an analysis of the 30-day risk of influenza-like illness and respiratory outcomes in persons for whom some household members (index cases) have had a medical visit associated with a diagnosis of influenza. The exposed individuals to the index case will be categorized into one of four cohorts according to whether the exposed person received prophylactic Relenza or no antiviral treatment and by whether the index family member with a diagnosis of influenza received antiviral treatment.Estimates of the direct effect of Relenza prophylaxis, the indirect effectof preventing disease in susceptible family members, and the total effect of disease reduction when both index cases and susceptible family members are treated will be obtained from different comparisons between cohorts, as outlined below.The research will cover the first three influenza seasons during which Relenza has been indicated for prophylactic use in the United States. These will be from October through April of 2006-2009.