MedImmune has announced preliminary data from a Phase III study indicating that CAIV-T (cold adapted influenza vaccine, trivalent) showed a statistically significant reduction (55 percent) in influenza illness caused by any influenza strain compared to the injectable influenza vaccine (TIV). The influenza attack rate was 8.6 percent for study participants receiving TIV compared to 3.9 percent for those who received CAIV-T. CAIV-T is MedImmune's investigational, refrigerator-stable formulation of FluMist, a frozen vaccine currently approved to prevent influenza in healthy children and adolescents, 5 to 17 years of age, and healthy adults, 18 to 49 years of age.
The trial was a randomized, double-blind study designed to assess the safety and relative efficacy of CAIV-T and TIV in children ages 6 months through 59 months during the 2004-2005 influenza season. The primary endpoint of the trial was culture confirmed influenza-like illness, caused by wild type strains antigenically matched to the vaccine. The study enrolled 8,492 children and was conducted at 249 sites in 16 countries in North America, Europe and Asia. Participants were randomized one-to-one to receive either CAIV-T or the injectable influenza vaccine. Each child also received a placebo nasal spray or placebo injection to preserve the double-blind design of the study. Participants were followed through the influenza season and evaluated to identify illnesses caused by influenza virus and for safety.