WASHINGTON - Next year's flu vaccine is getting an overhaul to provide protection against three new and different influenza strains - with hope it is better protection than this year's version.
Advisers to the Food and Drug Administration unanimously backed the new recipe yesterday, 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. Nancy Cox, 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 that the vaccine is a good match for only about 40 percent of the virus spreading in the United States.
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 yesterday'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 has a good record: 16 of the last 19 flu seasons had well-matched vaccines.
Still, "as we always say, influenza is quite unpredictable," Cox cautioned yesterday.