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Phase 3 Study Shows Cold Adapted Influenza Vaccine, Trivalent Is More Effective Than Trivalent Injectable Vaccine
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 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® (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.
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.
Source: MedImmune, Inc.