Phase 3 Study Results Of MedImmune, Inc.'s Next-Generation Influenza Vaccine Suggest Better Relative Efficacy Against Matched And Mismatched Strains Compared To The Flu Shot In Young Children

SAN FRANCISCO, May 1 /PRNewswire-FirstCall/ -- MedImmune, Inc. announced data from a pivotal Phase 3 study that showed its next-generation, investigational influenza vaccine, CAIV-T (cold adapted influenza vaccine, trivalent), was 55 percent more effective than the trivalent injectable inactivated influenza vaccine (TIV) in reducing influenza illness caused by any influenza strain in children 6 months to 59 months of age. The influenza attack rate was 8.6 percent for study participants receiving the flu shot compared to 3.9 percent for those who received CAIV-T (P <0.001). The data also showed that CAIV-T provided statistically significant improvements in reducing influenza illness caused by both matched and mismatched A strains as compared to the flu shot. The results are being presented today at the annual meeting of the Pediatric Academic Societies (PAS) in San Francisco, CA.

“The objective of this CAIV-T trial was to demonstrate better and broader protection against influenza illness compared to the flu shot in young children,” stated Robert Walker, MD, vice president, clinical development. “We anticipate submitting these data to the U.S. Food and Drug Administration (FDA) by the end of June 2006 to seek an expansion of our label to include children from 5 years down to 6 months of age. We continue to believe that our live, attenuated, needle-free influenza vaccine offers an important option to people wanting to protect themselves and their family against influenza disease.”

Entitled, “Comparison of the Efficacy and Safety of Cold-Adapted Influenza Vaccine, Trivalent With Trivalent Inactivated Influenza Vaccine in Young Children 5 to 59 Months of Age,” the Phase 3 pivotal study included 8,475 children at 249 sites in 16 countries in North America, Europe, the Middle East and Asia. Study participants were randomized one-to-one to receive either CAIV-T or the flu shot during the 2004-2005 influenza season. Each participant 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. The trial included more than 6,300 previously unvaccinated children with nearly 50 percent of those children less than 2 years of age.

In the trial, CAIV-T was 44-percent more effective than the flu shot against illness caused by influenza strains matched to the vaccines, which was the primary endpoint for the trial (attack rates: TIV = 2.4 percent, CAIV-T = 1.4 percent; P<0.001). Data also showed CAIV-T was 89-percent more effective than the flu shot in reducing influenza illness caused by the matched H1N1 A strain (attack rates: TIV = 0.7 percent, CAIV-T = 0.1 percent; P<0.001) and 79-percent more effective than the flu shot against the circulating mismatched H3N2 A strain (attack rates: TIV = 4.5 percent, CAIV-T = 1.0 percent; P<0.001). There were no cultures of mismatched H1N1 strains or matched H3N2 strains detected in the trial. While there were 16-percent fewer children with illnesses associated with B strains in the CAIV-T group compared to TIV (attack rates: TIV= 3.5 percent, CAIV-T = 3.0 percent), this difference was not statistically significant. Mismatch occurs when an influenza strain that circulates during the season varies significantly from the strain selected for use in the seasonal influenza vaccines. Significant vaccine mismatch has occurred in four of the last nine influenza seasons, including the 2004-2005 season when the Phase 3 trial for CAIV-T was conducted.

In the study, the overall incidence of adverse events and serious adverse events was similar in both groups except for a higher incidence of runny nose and nasal congestion in CAIV-T recipients (2.5 - 5.6 percent increase) and a higher incidence of injection site reactions in those receiving the flu shot (3.6 - 7.6 percent increase). There were no significant differences through the whole study period for all reported wheezing or for medically significant wheezing (MSW), a pre-specified safety endpoint. Previously unvaccinated children between 6 and 23 months of age had a small but statistically significant increase in MSW at 42 days following their first dose (2.0 percent for TIV vs. 3.2 percent for CAIV-T). Statistically significant differences were not seen beyond 42 days after this first dose nor at any time after the second dose.

“This head-to-head study and its data represent an important milestone in the development of a live, attenuated, needle-free influenza vaccine, particularly for children,” said Robert B. Belshe, M.D., director, Center for Vaccine Development at Saint Louis University School of Medicine, and chair of the study’s advisory committee. “We discovered that CAIV-T was significantly more effective in protecting children against influenza infection. This is especially important because this age group is among the most vulnerable to influenza infection, and they tend to spread influenza to other family members.”

The importance of vaccinating young children against influenza was recently underscored by the U.S. Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices’ new guidelines that recommend all children 6 months to 5 years of age be immunized against influenza. Since influenza disease is the leading cause of vaccine-preventable death throughout the U.S., increasing influenza vaccination rates, particularly among children, may help to reduce the incidence of disease in vaccinated individuals as well as the larger community.

Two additional CAIV-T studies presented at the PAS meeting reinforced the efficacy and safety profile of the vaccine, including:

* “Safety and Tolerability of Cold-Adapted Influenza Vaccine, Trivalent (CAIV-T) in Healthy Young Infants.” This safety study showed that CAIV-T was well tolerated in healthy young infants 6 weeks to 24 weeks of age. * “Comparative Immunogenicity of Frozen and Refrigerator-Stable Formulations of Live Attenuated Influenza Vaccine in Healthy Subjects.” Data from this comparative immunogenicity, safety and tolerability study of refrigerator-stable CAIV-T and frozen FluMist(R) (Influenza Virus Vaccine Live, Intranasal) showed that both formulations are well- tolerated and consistent with results from previous trials. The study included 376 participants 5 to 8 years of age and 566 participants 9 to 49 years of age. The immune response rates were similar in both age groups for each of the three seasonal influenza vaccine strains. Data from this study was included in MedImmune’s supplemental biologics license application, which was submitted to the FDA in September 2005 to show immunogenic equivalency of FluMist and CAIV-T. About FluMist

FluMist is indicated for active immunization for the prevention of disease caused by influenza A and B viruses in healthy children and adolescents, 5 to 17 years of age, and healthy adults, 18 to 49 years of age. There are risks associated with all vaccines, including FluMist. Like any vaccine, FluMist does not protect 100 percent of individuals vaccinated. In studies of people between the ages of 5 and 49 years, runny nose was the most commonly reported side effect. Other common side effects included various cold-like symptoms, such as headache, cough, sore throat, tiredness/weakness, irritability, and muscle aches.

FluMist should not be used, under any circumstances, in anyone with an allergy to any part of the vaccine, including eggs; in children and adolescents receiving aspirin therapy; in people who have a history of Guillain-Barre syndrome; and in people with known or suspected immune system problems. Pregnant women and people with certain medical conditions, asthma, or reactive airways disease should not get FluMist.

Please see the Prescribing Information at , visit , or call 1-877-633-4411 for additional information.

About MedImmune, Inc.

MedImmune strives to provide better medicines to patients, new medical options for physicians, rewarding careers to employees, and increased value to shareholders. Dedicated to advancing science and medicine to help people live better lives, the company is focused on the areas of infectious diseases, cancer and inflammatory diseases. With more than 2,200 employees worldwide, MedImmune is headquartered in Maryland. For more information, visit the company’s website at .

This announcement contains, in addition to historical information, certain “forward-looking statements” regarding the results of clinical trials for FluMist and CAIV-T. Such forward-looking statements are based on current expectations and involve inherent risks and uncertainties, including factors that could delay, divert or change current expectations and could cause actual outcomes and results to differ materially from current expectations. In addition to risks and uncertainties discussed in MedImmune’s filings with the U.S. Securities and Exchange Commission, no assurance exists that development efforts for CAIV-T will succeed, that CAIV-T will receive required regulatory approval or that, even if regulatory approval is received, CAIV-T will be commercially successful. MedImmune undertakes no obligation to update any forward-looking statement, whether as a result of new information, future events or otherwise except as may be required by applicable law or regulation.

MedImmune, Inc.

CONTACT: Media: Clarencia Stephen, +1-301-398-4073, Investors: Pete Vozzo,+1-301-398-4358, both of MedImmune, Inc.