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Preliminary Data From CAIV-T Trial Suggest Clinical Efficacy Over Flu Shot
"This pivotal trial is the third Phase 3 trial of CAIV-T to show statistically significant reductions in influenza disease compared to the injectible influenza vaccine. Collectively, these data suggest better efficacy against matched and mismatched strains and against both A and B strains," said David M. Mott, president and chief executive officer. "Our objective now is to complete our analyses and prepare the data for submission, for which we will request priority review designation, to the U.S. Food & Drug Administration (FDA) in the second quarter of 2006. If approved by the FDA, we hope to have the opportunity to offer CAIV-T as an alternative to the injectable influenza vaccine beginning in the 2007 influenza season."
MedImmune's pivotal Phase 3 trial for CAIV-T 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 (ILI), based on a modified version of the U.S. Centers for Disease Control & Prevention definition, caused by wild type strains antigenically matched to the vaccine. CAIV-T showed a 44-percent reduction in the number of these cases, compared to TIV (p less than 0.001). For matched strains, the attack rate was 2.4 percent for study participants receiving TIV compared to 1.4 percent for those receiving CAIV-T (p less than 0.001). The trial also met its secondary efficacy endpoints, with CAIV-T showing a 58-percent reduction in modified ILI caused by antigenically mismatched wild type strains. In the case of mismatched strains, the attack rate was 6.2 percent for the TIV arm and 2.6 percent for the CAIV-T group (p less than 0.001).
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.
The rates of serious adverse events and adverse events were similar in the two groups. As expected, runny/stuffy nose occurred more frequently in CAIV-T recipients and site of injection events occurred more frequently among TIV recipients. In the analyses of medical significant wheezing, the only statistically significant difference was observed in children not previously vaccinated under two years of age after the first dose. In this analysis, the rate in the CAIV-T arm was 3.2 percent versus 2.0 percent in TIV recipients. In this same population, no significant difference was observed beyond 42 days after the last vaccination.
"Influenza is an important cause of morbidity and mortality in children. FluMist has previously been shown to be highly effective in placebo-controlled trials," commented Edward M. Connor, M.D., executive vice president and chief medical officer. "This study provides important additional information about live, intranasal vaccination in young children, including meaningful reductions in influenza disease when compared with TIV in a season when both matched and mismatched viruses were circulating. In addition, the expanded safety data provided by this trial allows comprehensive assessment of benefit and risk for the two vaccines."
Prior Comparative Phase 3 Clinical Trials with CAIV-T and TIV
Two previously completed Phase 3 studies have been conducted comparing CAIV-T to TIV. In one study (514) approximately 2,200 infants and children six months through 71 months of age with a history of recurrent respiratory tract infections received either two intranasal doses of CAIV-T or two doses of TIV to compare the efficacy and safety of the vaccines. Children receiving CAIV-T in this study had a 53-percent reduction in culture-confirmed influenza compared to those receiving TIV. In a second trial (515), approximately 2,200 children and adolescents from six years through 17 years of age with a history of asthma received either one intranasal dose of CAIV-T or one traditional dose of TIV prior to the 2002-2003 flu season. Children receiving CAIV-T in this study had a 35-percent reduction in culture-confirmed influenza compared to those receiving TIV. In both trials, no significant differences were observed in the rates of wheezing post-vaccination.
Other Recent Progress with Influenza Franchise
MedImmune recently completed a study evaluating the safety and immunogenicity of FluMist when given concurrently with measles-mumps-rubella (MMR) and varicella vaccines in 1,245 healthy children ages 12 months through 15 months. Co-administration of these vaccines did not interfere with immune responses to any vaccine included in the trial.
In September 2005, MedImmune submitted a supplemental Biologics License Application (sBLA) with the FDA for approval to use CAIV-T in preventing influenza in healthy individuals 5 to 49 years of age. Included in the sBLA were data from a recently completed pivotal Phase 3 study comparing the immunogenicity of FluMist and CAIV-T, as well as additional preclinical and clinical data supporting the comparability of the two formulations.
MedImmune also recently announced that it is working with the National Institutes of Health under a Cooperative Research and Development Agreement to produce and test attenuated, live intranasal influenza vaccines against pandemic influenza strains. This effort will use MedImmune's proprietary reverse genetics technology, which allows researchers to remove potentially pathogenic portions of a pandemic virus, thereby making the vaccine and its production safer. In the interest of public health, MedImmune has offered licenses for its reverse genetics technology to U.S. and international health authorities and other vaccine manufacturers developing pandemic influenza vaccines.
Source: MedImmune, Inc.