Children Vaccinated With FluMist Nasal Spray Have Fewer Cases of Flu
FluMist to Help Protect Against Matched, Drifted Strains
According to pivotal Phase 3 research published in the February 15, 2007 issue of The New England Journal of Medicine, children under 5 years of age immunized with FluMist (Influenza Virus Vaccine Live, Intranasal) reported 55 percent fewer cases of influenza compared to children who received the flu shot. In the study, FluMist also demonstrated protection against influenza strains that were both matched and mismatched to the vaccine. The study of 8,475 children, 6 months to 59 months of age, was conducted at 249 sites across the United States, Europe, Asia and the Middle East by MedImmune, Inc. (NASDAQ: MEDI) .
"With only one influenza vaccine currently approved for use in children under the age of 4, options are limited and sometimes hard to come by," said lead author Robert B. Belshe, M.D., director of the Center for Vaccine Development at the Saint Louis University School of Medicine. "This research gives us important insight into how we might help protect these vulnerable young children in the future. In this study, half as many cases of influenza were observed in the group of children who received the intranasal mist, and we also saw that they were broadly protected against circulating flu strains that were not matched to the flu strains in that season's vaccines."
The study utilized the recently-approved refrigerated formulation of FluMist, known in the clinical setting as CAIV-T (cold adapted influenza vaccine-trivalent). The U.S. Food and Drug Administration (FDA) approved MedImmune's supplemental Biologics Licensing Application (sBLA) for the refrigerated formulation of FluMist on January 5, 2007. MedImmune conducted this pediatric study during the 2004-2005 influenza season and submitted results in July 2006 to the FDA as the basis of a pending request to expand the age indication for FluMist to include children as young as one year of age who do not have a history of wheezing or asthma. FluMist is currently indicated for healthy children and adolescents 5 to 17 years of age and healthy adults 18 to 49 years of age.
"Our primary objective in the study was to determine how FluMist would perform against the flu shot in young children, and to assess the comparative safety outcomes to help us determine for whom FluMist might be most beneficial in the pediatric population," said Edward M. Connor, M.D., MedImmune's executive vice president and chief medical officer. "A careful evaluation of the benefits and risks associated with FluMist in this study demonstrated that FluMist was highly favorable for the nearly 80 percent of the children 12 to 59 months of age who did not have a history of wheezing or asthma."
In the trial, children 6 months to 59 months of age were randomly assigned to receive either FluMist or the flu shot. In the double-blind trial, each study participant received one of the actual vaccines along with a saline injection or saline intranasal spray placebo. As is recommended for this age group, children who had not been previously vaccinated were given a second dose of vaccine along with an additional placebo 28 to 42 days after the first dose. Throughout the flu season, nasal swabs were obtained from children reporting any flu-like illness to culture for possible influenza as defined by the study protocol.
Overall, there were 185 (55 percent) fewer cases of culture-confirmed influenza in the group receiving FluMist compared to those receiving the shot. FluMist demonstrated protection against influenza A viruses well-matched to those in the vaccine (89 percent fewer cases caused by matched H1N1 viruses in children receiving FluMist vs. the flu shot), as well as those mismatched to the vaccine virus (79 percent fewer cases caused by mismatched H3N2 viruses in children receiving FluMist vs. the flu shot). In addition, while not statistically significant, FluMist showed 27 percent fewer cases caused by matched influenza B strains compared to the flu shot. No difference among the vaccines was observed against mismatched B strains.
Generally, both vaccines were well-tolerated. In children 6 to 11 months of age, FluMist was associated with statistically significantly more hospitalizations for any cause. A non-significant trend toward more hospitalizations in the FluMist group was seen in children 12 months to 47 months of age with a past history of wheezing. These observations require additional study. Until further information is available, MedImmune is presently not seeking an indication for children under 12 months of age or for children 12 months to 59 months of age who have a past history of wheezing illness. In children 12 months to 59 months of age without a past history of wheezing, there was a trend (though not statistically significant) in the opposite direction in that there were fewer hospitalizations in children who received FluMist compared to the flu shot. In children 12 months to 59 months of age without a past history of wheezing, the rates of wheezing were not statistically different in children who received FluMist (4.7 percent) compared to the flu shot (4.9 percent).
FluMist is currently 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. As with any vaccine, FluMist does not protect 100 percent of individuals vaccinated and may not protect against viral strains not contained in the vaccine.
Under no circumstances should FluMist be administered as an injection (i.e., parenterally). FluMist is contraindicated in persons with hypersensitivity to any component of the vaccine, including eggs; in children and adolescents receiving aspirin therapy or aspirin-containing therapy; in individuals with a history of Guillain-Barre syndrome; and in individuals with known or suspected immune deficiency. The safety and efficacy of FluMist have not been established in pregnant women or for patients with chronic underlying medical conditions, including asthma or reactive airways disease; the vaccine should not be administered to these patients.