Preliminary Data from CAIV-T Pivotal Phase 3 Trial Demonstrate Clinical Efficacy Over Flu Shot in Head-to-Head Influenza Study

GAITHERSBURG, Md. -- MedImmune, Inc. today announced preliminary data from a Phase 3 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 (p less than 0.0001).

CAIV-T is MedImmune's investigational, refrigerator-stable formulation of

FluMist (Influenza Vaccine Live, Intranasal), 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.

"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 and 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 Centers for Disease Control and Prevention (CDC) 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 2 years of age after the first dose.  In this analysis, the rate in the CAIV-T arm was 3.2 percent vs. 2.0 percent in TIV recipients.

In this same population, no significant difference was observed beyond 42 days after the last vaccination.

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.

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.