Spray vaccine is more effective than flu shot
WASHINGTON — Spraying flu vaccine into the noses of babies
and preschoolers offers significantly more protection than shots,
says one of the largest comparisons of flu inoculations ever performed.
The study, being presented Monday at a child-health meeting, found
the 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 government
approval to sell FluMist for younger children as well.
But to flu experts, 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 youngsters or adults.
And children are the prime spreaders of flu virus, fueling 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 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
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 asthma-like
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 Belshe still 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
Belshe and colleagues in 16 countries enrolled youngsters 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 salt water, to allow unbiased comparison.
By winter’s end, just 3.9 percent of nasal-spray recipients
also got sick with influenza, compared with 8.6 percent of shot
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.
“It’s clear that FluMist is an influenza vaccine whose
potential has not yet been either reached or appreciated,”
said Dr. William Schaffner of Vanderbilt University, a vaccine expert
who wasn’t involved in the study.
Easier administration aside, it “apparently provides broader
protection than does the injected vaccine,” Schaffner added.
“That’s really very, very exciting because we all know
the influenza virus has a tendency to drift,” or mutate.
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 body-wide. Flu shots,
made with dead influenza virus, don’t give the extra nose
So while flu shots are good at boosting previous immunity in healthy
people who’ve caught flu before or been inoculated many times,
more immune-naive babies and preschoolers may need that more flu-like
nasal response, Belshe said.
His study didn’t use the exact version of FluMist sold today,
but one slightly altered so that it requires refrigerator instead
of freezer storage.
Apart from regular winter flu, the government is experimenting with
brewing FluMist for bird flu, just in case the worrisome H5N1 strain
ever begins spreading easily among people. The theory is that the
extra nasal reaction might prove more protective there, too.
It makes sense, Belshe said. “When it comes to pandemic flu,
we’re all behaving like young children — we’re