- The Washington Times - Monday, May 1, 2006


Spraying flu vaccine into the noses of babies and preschoolers, prime spreaders of the virus, offers significantly more protection than shots, according to one of the largest comparisons of flu inoculations.

The study, presented yesterday at a child-health meeting, found that the spray vaccine was 55 percent more effective than traditional flu shots when given to nearly 8,000 children younger than 5.

The nasal spray FluMist, the only flu vaccine made of live but weakened influenza viruses, is sold only for children 5 or older. Manufacturer MedImmune Inc., which funded the research, plans to seek government approval to sell FluMist for younger children as well.

But to flu specialists, the findings have important public health implications. Doctors have long known that flu shots don’t work quite as well in very young children as they do in older children or adults.

And children fuel infections in older people, who may not survive. Each winter, flu kills 36,000 Americans, most of them elderly.

“Our current thinking is that to control influenza, we really have to vaccinate all children,” said Dr. Robert Belshe, a prominent vaccine specialist at Saint Louis University who led the study.

“Anything that makes it easier and more effective [to vaccinate] children is going to contribute a lot to the protection against influenza.”

The study did find a safety concern: A few of the very youngest patients, those ages 6 months to 2 years, had an episode of asthmalike wheezing in the weeks after the first FluMist dose.

The increased risk was slight — 1 percent more children wheezed after FluMist than after flu shots — and the reaction was temporary. But Dr. Belshe is analyzing whether the risk would offset the increased flu protection, and regulators undoubtedly will ask whether it means FluMist should be used only after age 2.

Dr. Belshe and colleagues in 16 countries enrolled children ages 6 months to 5 years during the 2004 flu season. Every child got both a nasal spray and a shot, but only one was the real vaccine instead of saltwater, to allow unbiased comparison.

By winter’s end, 3.9 percent of nasal-spray recipients got sick with influenza, compared with 8.6 percent of shot recipients.

More intriguing: That winter, a slightly different strain than was in the vaccine began circulating, and the nasal spray was more protective against that new strain, too.

“That’s really very, very exciting because we all know the influenza virus has a tendency to drift,” or mutate, said Dr. William Schaffner of Vanderbilt University, a vaccine specialist who wasn’t involved in the study.

Why, biologically, might FluMist work better in tots?

The live-virus nasal spray mimics real flu infection by stimulating immune defenses first in the nose and then bodywide. Flu shots, made with dead influenza virus, don’t give the extra nasal reaction.

So although flu shots are good at boosting immunity in healthy people who’ve caught flu before or been inoculated many times, more immune-naive babies and preschoolers may need that more flulike nasal response, Dr. Belshe said.



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