GAITHERSBURG, Md. — A long-awaited painless flu vaccine suffered a setback Friday as government scientists said there are too many safety questions for Aviron Inc.'s nasal vaccine to be sold yet.
Advisers to the Food and Drug Administration said FluMist clearly can protect against the flu and probably one day will prove safe enough for certain Americans to use. But unlike today's flu shots, FluMist is made with live influenza virus, so the nation needs more proof that squirting live virus into people's noses — especially the toddlers who would be prime targets — is safe, panelists concluded after two days of debate.
Concerns include how well FluMist combines with other vaccines that toddlers receive, and whether there might be a rare risk of pneumonia or asthma among certain children.
The FDA is not bound by its advisers' recommendations but typically follows them.
Aviron had hoped to begin selling limited supplies of FluMist in time for this year's flu season, offering the first needle-free vaccine alternative to healthy people ages 1 to 64. (Studies of FluMist in the elderly and people with diseases that make them particularly vulnerable to flu complications still are under way.)
Aviron chief executive C. Boyd Clarke said the company now hopes to answer the panel's safety questions in time for FluMist to be used in the 2002-2003 flu season.
Many doctors have eagerly awaited the spray vaccine, saying the pain-free method would encourage more people to get vaccinated. About 70 million get today's flu vaccine, a shot in the arm, each year. Yet influenza still kills 20,000 Americans each year and hospitalizes about 100,000. Young children in particular are the primary spreaders of flu to parents, grandparents and caregivers, yet they rarely receive annual shots.
FluMist does work, the FDA's advisers said Friday. It was roughly 93 percent effective in children 15 months or older, the panelists agreed; about half the advisers said it wasn't proved effective in younger children.
A study in healthy adults didn't prove FluMist cut the incidence of flulike illnesses, but it did lower severe illness by about 19 percent.
But safety questions remain around the vaccine, the FDA advisers said.
"I feel the overall safety profile is very good," said Dr. Nancy Cox, influenza chief at the Centers for Disease Control and Prevention. But, "there's no doubt in my mind there's some real-world issues that have to do with safety that need to be dealt with."
"This is a new way of dealing with children, and you vaccinate them every year," so there must be more data proving safety, added Judith Goldberg of the New York University School of Medicine.
Among the concerns:
—Aviron had no data showing it's safe for children to get FluMist at the same time they also get other vaccines, including the measles, mumps, rubella and chickenpox immunizations.
—FDA scientists spotted some rare cases of pneumonia among the thousands of children given FluMist — 37 cases, compared to 12 pneumonia cases found so far among children who got a dummy spray. They aren't sure if it's a coincidence or a risk, but FDA medical reviewer Dr. ChrisAnna Mink called it "a signal, and we need to understand more."
—Because a different type of flu strikes every year, people must be vaccinated each year — yet Aviron hasn't studied repeated annual doses.
—FluMist isn't supposed to be given to anyone with asthma. But some asthmatic children did get it during testing anyway, and scientists asked if a handful of subsequent asthma attacks were possibly related to the vaccine.
—No one yet knows if FluMist would work as well as today's flu shots. What would happen, some panelists asked, if the people most at risk for flu's complications, such as the elderly or people with lung diseases, persuaded doctors to give them FluMist even though Aviron hasn't finished studying how well it works in such groups?
On the Net: Food and Drug Administration: www.fda.gov