U.S. prescribes new recipe for flu shot

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U.S. prescribes new recipe for flu shot

Updated Thu. Feb. 21 2008 6:10 PM ET

The Associated Press

WASHINGTON -- Next year's flu vaccine is getting a complete overhaul to provide

protection against three new and different influenza strains -- hopefully better

protection than this year's version.

Advisers to the Food and Drug Administration unanimously backed the new recipe

on Thursday, echoing an earlier decision by the World Health Organization. It's

a highly unusual move: Seldom are more than one or two strains swapped out from

one year to the next.

Now the question is whether vaccine manufacturers can make such a big change in

time to produce more than 100 million doses by the fall.

" It's going to be a really busy spring and summer, and of course we're always

looking for fallback positions just in case things don't work out well, " said

Dr. , flu director at the Centers for Disease Control and Prevention.

" There's a lot of work that will be going on ... to try and make sure that

everything comes together in such a way that there will be plenty of vaccine. "

One concern: A strain called Brisbane/10 that's responsible for much of this

winter's misery doesn't grow very quickly in the laboratory, potentially

complicating already laborious vaccine production.

The flu vaccine must be reformulated every year to keep up with the

fast-evolving influenza virus, and this year the government made a rare wrong

bet on which strains would cause the most disease. The flu season got off to a

slow start, but it rocketed in mid-January as some new strains arrived -- and

the CDC found the vaccine is a good match for only about 40 percent of the virus

now spreading in the U.S.

That Brisbane/10 strain is the big culprit, one first spotted in Australia late

last winter, too late for scientists to include in this year's vaccine recipe

even if they had predicted it would gain steam.

Flu viruses come in different strains that constantly mutate, until one that few

people have immunity against emerges and is able to spread widely. Each year's

vaccine contains protection against two varieties of the harsher Type A flu --

subtypes known as H1N1 and H3N2 -- and one from the more benign Type B family.

CDC and international authorities expect Brisbane/10, a version of the H3N2 flu,

to still be around next year. They predict a second new Type A strain, known as

H1N1/Brisbane/59, also will hit, along with a newer Type B/Florida strain,

prompting Thursday's decision to put all three in next year's vaccine.

It's a gamble based on tracking illness around the globe, and the CDC does have

a pretty good record: 16 of the last 19 flu seasons had well-matched vaccines.

Still, " as we always say, influenza is quite unpredictable, " cautioned

Thursday.

The recipe must be set about eight months before manufacturers start shipping

doses because flu vaccine production is so complex. Health authorities come up

with seed stocks of the virus strains that manufacturers then must grow in

chicken eggs.

Makers of vaccine for the Southern Hemisphere already have added the troublesome

Brisbane/10 strain to their own shots, and found it doesn't grow easily.

Scientists now are working on a solution to that technical problem, such as

using a very similar virus -- it's even called " Brisbane/10-like " -- found in

Uruguay that would provide the same protection, said.

" It's certainly a challenge for all the manufacturers, " said Kavanaugh of

Medimmune Inc., which makes a nasal spray flu vaccine, the only non-shot

version. " We're working with three new strains. ... There's some unknowns

related to those and how they're going to grow. "

As for the rest of this winter, the CDC says the current vaccine should provide

some protection, perhaps resulting in a milder case of flu than if someone

hadn't been inoculated. It's too early to tell if this winter's flu will be more

deadly than usual. Every year, the flu infects up to 20 percent of the

population, hospitalizes 200,000 people and kills 36,000.

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