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Influenza :: Nasal spray flu vaccine reduces influenza attack rate

Nasal spray flu vaccine reduces the influenza “attack rate” in children by 55 percent when compared with a group of children who received the traditional flu shot in the arm or thigh.

“Children get the flu twice as often as adults,” said Robert Belshe, M.D., a vaccine researcher at Saint Louis University School of Medicine and the lead author of the study. “It’s important to vaccinate kids against influenza — and to identify new and more effective flu vaccine options — because kids have a higher attack rate for influenza infection than adults. And children, when they bring the illness home, tend to pass it on to adults in their household.”

The attack rate is the number of people who get sick as measured against the total number of people in a particular study population.

Belshe said the study points to new thinking about how to best protect very young children from influenza and offers insight into the safety and efficacy of influenza vaccines for children, whether administered through the nose or with a needle.

The study published in the New England Journal of Medicine was conducted in 8,475 children between the ages of 6 months and 5 years at 249 sites in 16 countries and was funded by MedImmune, Inc. It is the largest ever pediatric study comparing a nasal spray flu vaccine head-on with the traditional flu shot. About half of the children in the study received an FDA-approved injectable flu vaccine (which contains an inactivated flu virus), and the other half received a refrigerated version of the nasal spray influenza vaccine. The nasal spray influenza vaccine FluMist? (Influenza Virus Vaccine Live, Intranasal) is currently FDA-approved for use in healthy people between 5 years and 49 years.

“We compared the attack rate of the flu in children who were randomized to receive either the traditional shot or the FluMist nasal spray — for the entire 2004-2005 winter season,” Belshe said. “In this worldwide trial, the nasal spray flu vaccine reduced culture-confirmed influenza disease by 55 percent compared to the flu shot.”

Belshe said the traditional flu shot and the nasal spray flu vaccine stimulate different types of immune responses. Whereas the flu shot stimulates antibodies in the blood, the nasal spray vaccine stimulates antibodies both in the bloodstream and in the nose, and may stimulate a cellular immune response as well.

“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. The nasal spray flu vaccine appears to induce a more complete immune response,” Belshe said.

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