The nasal spray flu vaccine FluMist proved to be more effective than traditional flu shots in a large, worldwide study funded by the vaccine's manufacturer, MedImmune Inc. The nasal vaccine reduced flu cases by 55 percent compared with the flu shot.
The study, which included nearly 8,000 children between the ages of 6 months and 5 years, is published in the Feb. 15 issue of The New England Journal of Medicine.
"For the majority of children it appears that the nasal vaccine is a better choice," researcher Robert B. Belshe, M.D., of Saint Louis University, tells WebMD.
FluMist is approved only for children over the age of 5 years and for adults under age 50. But based on the newly reported findings, MedImmune has petitioned the FDA to approve the nasal vaccine for children between the ages of 1 and 5 years old who do not have a previous history of wheezing and asthma.
The company is not seeking approval for children younger than 1 year. Children in the study between the ages of 6 months and a year who got the nasal vaccine had more hospitalizations in the six months following vaccination than children who got the traditional flu shot vaccine.
Belshe calls the hospitalizations "puzzling." He adds that more research is needed to determine if the nasal vaccine is safe for children less than 1 year old.
"For children who are younger than a year, the flu shot remains the preventive vaccine of choice, even though it didn't work as well to prevent the flu," Belshe tells WebMD.
The traditional flu shot, used for half a century, is made from killed flu viruses, while FluMist is made from weakened live viruses.
The two vaccines also stimulate immune response in different areas. While the shot stimulates production of flu-fighting antibodies in the blood, the nasal spray vaccine stimulates production of antibodies in the blood and the nose, Belshe explains.
"The big difference is the induction of antibodies in the nose, which is important because this is where the flu virus usually enters the body," he says.
The newly reported study is the largest ever to compare the nasal spray flu vaccine head-to-head with the flu shot in children younger than 5. About half the children in the study got the killed flu shot, while the other half got the live nasal vaccine.
The study was conducted during the 2004-2005 flu season and included children living in 16 countries; 49 percent of participants were from the U.S. In all age groups tested, the FluMist vaccine proved more effective for preventing flu.
Children 6 to 11 months old had more hospitalizations after receiving the nasal vaccine. The researchers also noted an increased rate of hospitalization in children 6 months to 4 years old who had a history of wheezing and received the nasal spray vaccine.
The finding led to the decision to seek approval for the vaccine only for children over the age of 1 year with no known history of wheezing or asthma, MedImmune spokesman Frank J. Malinoski, M.D., Ph.D., tells WebMD.
A ruling on the latest request to approve the vaccine in young children is expected by late May. If approved, the vaccine should be available for use in children by July, in time for the 2007-2008 flu season, Malinoski says.
SOURCES: Belshe, R.B. The New England Journal of Medicine, Feb. 15, 2007; Vol. 356: pp. 685-696. Robert B. Belshe, M.D., professor of internal medicine and infectious diseases, Saint Louis University; director, Center for Vaccine Development, SLU Health Sciences Center, St. Louis. Frank Malinoski, M.D., Ph.D., senior vice president of medical and scientific affairs, MedImmune Inc.
By Salynn Boyles
Reviewed by Louise Chang, M.D