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November 15, 2004

MedImmune Initiates Phase 3 Study for Numax(TM) in Native American Infants

GAITHERSBURG, Md., Nov. 15 /PRNewswire-FirstCall/ -- MedImmune, Inc. (Nasdaq: MEDI) today announced that it has initiated a Phase 3 study to evaluate the safety and efficacy of Numax in reducing respiratory syncytial virus (RSV) disease in healthy full-term Native American (Navajo and White Mountain Apache) infants. Recently accumulated epidemiological data indicate that the risks associated with RSV disease for otherwise healthy, full-term Native American infants is similar to those commonly associated with children considered to be at high-risk to the virus, including children born prematurely or with chronic lung disease or congenital heart disease. In addition to the risk from RSV itself, Native American children have a high rate of wheezing and asthma.

"By conducting this Phase 3 study, we hope to determine if Numax can play a role in reducing the burden of RSV disease among these Native American infants," said Edward M. Connor, executive vice president and chief medical officer. "Moreover, we will monitor the children enrolled in this study until they reach five years of age, and collect valuable data on whether reducing RSV disease with Numax in the first two years of life can reduce the incidence of wheezing and prevent the development of asthma in full-term healthy children."

The Native American Phase 3 study of Numax is a randomized, double-blind, placebo-controlled trial that will enroll approximately 3,000 Navajo and White Mountain Apache infants over four RSV seasons. All children in the study will receive a maximum of five monthly intramuscular injections of Numax (15 mg/kg) or placebo during the RSV season for two consecutive seasons. During the first year, plans are to enroll approximately 450 infants and assess the study's overall operational feasibility.

In addition to the Native American trial, MedImmune also recently announced that it had initiated a Phase 3 study comparing the safety and efficacy of Numax in reducing RSV disease in high-risk infants to that of Synagis(R) (palivizumab), the current standard of care for reducing RSV hospitalizations in this population. In preclinical studies, Numax has been shown to be more potent than Synagis in reducing RSV replication in both the lower and upper respiratory tract when given at the same dose. The Numax comparative Phase 3 trial is designed to assess if the increased potency seen in preclinical studies can be translated into better efficacy against lower respiratory tract illness in high-risk children and to assess the effect of Numax on upper respiratory tract disease, such as otitis media.

About RSV and Synagis

RSV is the most common respiratory infection in infancy or childhood, resulting in over 125,000 hospitalizations in the U.S. annually in children less than one year of age. Approximately one-half of all infants are infected with RSV during the first year of life, and nearly all children have been infected at least once by the time they reach their second birthday. Children born prematurely as well as those with chronic lung disease or congenital heart disease are at highest risk of severe disease and hospitalization due to RSV.

Synagis is marketed for the prevention of serious lower respiratory tract disease caused by RSV in pediatric patients at high risk of RSV disease, which is prominent in the Northern Hemisphere from October through May. Synagis is a humanized monoclonal antibody given through a simple intramuscular injection once a month during the RSV season. Synagis was initially licensed by the FDA in 1998 to prevent RSV hospitalizations in high risk infants, and in 2003, its label was expanded to include safety and efficacy data supporting its use in young children with hemodynamically significant congenital heart disease to prevent hospitalization caused by RSV. For full prescribing information for Synagis, see the company's website at http://www.medimmune.com.

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 approximately 1,900 employees worldwide, MedImmune is headquartered in Maryland. For more information, visit the company's website at http://www.medimmune.com.

This announcement may contain, in addition to historical information, certain forward-looking statements that involve risks and uncertainties. Such statements reflect management's current views and are based on certain assumptions. Actual results could differ materially from those currently anticipated as a result of a number of factors, including risks and uncertainties discussed in MedImmune's filings with the U.S. Securities and Exchange Commission. The company is developing several products for potential future marketing. There can be no assurance that such development efforts will succeed, that such products will receive required regulatory clearance or that, even if such regulatory clearance were received, such products would ultimately achieve commercial success.

SOURCE  MedImmune, Inc.
    -0-                             11/15/2004
    /CONTACT:  Media: Jamie Lacey, +1-301-398-4035, or Investors: John Filler,
+1-301-398-4086, both of MedImmune, Inc./
    /Web site:  http://www.medimmune.com/
    (MEDI)

CO:  MedImmune, Inc.
ST:  Maryland
IN:  MTC HEA BIO
SU:  CHI

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