Washington ? Flu shots don’t protect babies and preschoolers quite as well as they do older children, but a new study suggests a spray flu vaccine may work better.

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

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

Flu experts say the findings have important public health implications. Each winter, flu kills 36,000 Americans, most of them elderly – and children are influenza’s prime spreaders.

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

In one of the largest comparisons of flu vaccine ever performed, Belshe and colleagues in 16 countries studied youngsters ages 6 months to 5 years during the 2004 flu season. Just 3.9 percent of nasal-spray recipients also became 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.