FluMist Found Safe and Efficacious in Younger Children

February 14, 2007

ST. LOUIS -- A live attenuated flu vaccine -- administered in a nasal spray -- outperformed the traditional inactivated vaccine in a large study of children from six months to five years old.

ST. LOUIS, Feb. 14 -- A live attenuated flu vaccine -- administered in a nasal spray -- outperformed the traditional inactivated vaccine in a large study of children from six months to five years old.

Among children given the live vaccine, there were 54.9% fewer cases of flu than among those who got the killed vaccine, according to Robert Belshe, M.D., of the Saint Louis University Health Sciences Center here.

The efficacy improvement was seen whether a child was infected by a flu strain well-matched to the vaccine or an antigenically drifted strain, Dr. Belshe and colleagues reported in the Feb. 15 issue of the New England Journal of Medicine.

Currently, children from six months to five years old are recommended to have a flu shot every year using the inactivated vaccine, which is administered as an intramuscular injection.

The live vaccine, administered in a nasal spray, is not yet approved for children under the age of five years.

The researchers enrolled more than 8,000 children in 16 countries and randomly assigned them to either the live or the inactivated vaccine from Oct. 20 to Oct. 29, 2004.

Vaccines used were FluMist, a nasal spray manufactured by MedImuune Inc., of Gaithersburg, Md., (which sponsored the study) and, depending on location, the inactivated vaccines Fluzone or Vaxigrip, both made by Aventis Pasteur. Saline placebos -- a nasal spray and an injection -- were used to preserve blinding.

The study found:

  • There were 153 cases of culture-confirmed flu in the FluMist group, compared with 338 cases among the children getting inactivated vaccine -- a difference that was statistically significant at P

That opinion was echoed by Nancy Cox, Ph.D., and Carolyn Buxton Bridges, M.D., of the CDC in Atlanta. Writing in an accompanying editorial, they said the results of the study are "encouraging."

But "further discussion and careful review of the safety data" are needed before developing any further guidance on the use of FluMist in younger children, they cautioned.

"It is critically important to evaluate the risks and benefits of annual immunization with the available influenza vaccines and to target their use to the populations that will have the greatest overall benefit," they said.