Enovirus, or parainfluenza virus 1 or 3. The study was conducted at 25 study sites in the Czech Republic (14 study sites) and Slovakia (11 study sites), with enrolment occurring between December 2014 and April 2015, and the last subject visit was on 03 June 2015. Detailed primary efficacy endpoints are provided in the Additional file 1.Inclusion criteriaMale and nonpregnant female RDX5791 supplier subjects aged 18 to 75 years with a clinical diagnosis of PubMed ID:https://www.ncbi.nlm.nih.gov/pubmed/27196668 ILI were included in this study. Influenza-like illnesses were defined as an oral temperature of at least 38 observed at the study site with at least 1 respiratory symptom of cough, sore throat, or nasal obstruction and at least 1 constitutional symptom of fatigue, headache, myalgia, or feverishness. The respiratory and constitutional symptoms were required to be considered by the subject as moderate or severe in intensity (a score of more than 1 on the 4point influenza-like symptoms assessment scale). The subjects were required to have experienced the onset of ILI no more than 36 h prior to screening, where onset is defined as the time when the subject experienced fever and at least 1 respiratory symptom and at least 1 constitutional symptom. The full inclusion criteria and Influenza-Like Symptoms Assessment Scale are detailed in the Additional file 1.A sample size of 258 subjects (129 subjects in each treatment group) in the modified intent-to-treat (mITT) analysis set with a total of 430 randomly assigned subjects was calculated using the log-rank test (inputting the median survival times). Sample size calculations were performed using PASS software Version 12 (NCSS, LLC, Kaysville, Utah, USA) and considered a statistical power of 80 to detect a clinically relevant difference between 3.5 days in the treatment group and 5 days in the placebo group. A 20 dropout rate was also considered, which meant that a final sample size of 206 subjects (103 subjects in each treatment group) would be required for the study. However, because of the challenges faced during enrolment, which included a late influenza alert and an unexpectedly mild influenza season, the decision was made to continue enrolment until 30 April 2015. A total of 463 subjects were randomly assigned, and of these, only 137 subjects met the criteria for inclusion in the mITT analysis set.Statistical analysisAll analyses were conducted using SAS?software Version 9.2 (SAS Institute Inc, Cary, North Carolina, USA). All statistical tests were 2-sided hypothesis tests performed with a 5 level of significance, which resulted in 95 (2-sided) confidence intervals (CIs). No adjustments for multiplicity were made. The hazard ratios (HRs) and 95 CIs were estimated using a proportional hazards model (HR >1 indicated a benefit to inosine pranobex compared with placebo). The safety analysis set consisted of all subjects who received at least 1 dose of any study drug. All analyses using the safety analysis set grouped subjects according to the treatment that the subjects had actually received. The mITT analysis set consisted of all randomly assigned subjects who had a positive laboratory confirmation of acute respiratoryBeran et al. BMC Infectious Diseases (2016) 16:Page 4 ofviral infection due to influenza A or B virus, RSV, adenovirus, or parainfluenza virus 1 or 3. This set was used for the primary and secondary efficacy analyses. Detailed primary efficacy endpoints are provided in the Additional file 1. All analyses using the mITT analysis set.