WASHINGTON (AP) - Government scientists gave a tentative endorsement to the first nasal-spray flu vaccine, while stressing that it's useful only for certain healthy people, not those most at risk of severe influenza.
Called FluMist, the long-awaited vaccine would be squirted up noses instead of injected into arms.
But advisers to the Food and Drug Administration cautioned Tuesday that if it's allowed to be sold, FluMist won't be for the people who need flu vaccination most: toddlers, the elderly and anyone with asthma or other chronic diseases.
Indeed, FluMist initially was created with the hope of giving toddlers a needle-free vaccine. Then researchers discovered it seems to increase the risk of asthma attacks in children under age 5.
So in its second attempt at winning FDA approval in two years, the vaccine's maker withdrew plans to sell FluMist for toddlers, saying it instead would target healthy people ages 5 to 64.
But the FDA's advisers endorsed only part of that plan Tuesday, recommending that FluMist be approved for sale just for people ages 5 to 49. They concluded there was too little evidence that FluMist protects people 50 and over, an age when the immune system begins to weaken.
As for people over 65, who are most at risk of dying from the flu, manufacturer MedImmune Inc. hasn't yet studied the nasal spray in that age group.
MedImmune, based in Gaithersburg, Md., wants to sell FluMist in time for next winter's flu season. But the question is whether the FDA, which isn't bound by its advisers' recommendations, will let a vaccine with so many restrictions be sold.
If so, those curbs would severely limit how often doctors would offer FluMist instead of the flu shots that 70 million Americans get every year.
A big unanswered question is whether FluMist is as good as a standard flu shot. FluMist is made of a weakened but live flu virus, while flu shots are made of killed virus. MedImmune hasn't compared the two vaccines.
Calling that question "the elephant in the room," FDA adviser Dr. Julie Parsonnet of Stanford University complained that without such data, doctors won't know which product to offer which patient.
"They are issues that are going to be highly problematic," agreed Dr. Dixie Snider of the federal Centers for Disease Control and Prevention.
Flu kills 20,000 Americans each year and hospitalizes 100,000. Those most at risk of flu complications are people over age 65 and anyone with certain illnesses, including asthma and heart disease. Also, this year for the first time, pediatricians are being encouraged to vaccinate babies and toddlers, who are hospitalized with flu as often as the elderly and are key spreaders of infection through day care and to elderly grandparents.
Flu experts have longed for a needle-free alternative as a way to persuade more people to get annual flu vaccinations.
The nasal vaccine works by stimulating the immune system through the same nose tissue where the flu virus attacks. But in July 2001, FDA's advisers blocked FluMist's sale, saying it wasn't yet proven safe for children.
Tuesday, MedImmune argued its case again.
The vaccine proved 93 percent protective against flu in a study of 1,600 healthy children ages 15 months to 6 years. Side effects primarily included runny nose, muscle aches and fever.
But up to 1.5 percent of children under age 5 who received FluMist suffered asthma attacks or asthma-like wheezing, rates almost four times higher than children who received a dummy vaccine, the FDA said.
The FDA's advisers agreed with MedImmune's subsequent decision to target FluMist only to children over 5, who didn't seem to have that asthma risk.
In adults, FluMist didn't work as well. In a study of 4,561 healthy, working adults ages 18 to 64, FluMist recipients were just as likely as people given a dummy vaccine to experience a flulike illness, although vaccination did cut severe illness by about 17 percent.
The FDA said FluMist didn't protect people ages 50 to 64 at all. MedImmune argued that those people didn't get as sick as the unvaccinated, but FDA's advisers ultimately said the company hadn't proved its case.
Another key concern is that sneezing children occasionally spread the FluMist virus, raising questions about whether the spray vaccine would endanger grandparents or asthmatic playmates who aren't inoculated.