Millions of doses of flu vaccine will expire at midnight June 30, unsold during this year's mild flu season and written off as trash. Still perfectly good, and possibly useful for a few more years, the vaccine will wind up being destroyed. This annual ritual is supposed to ensure that Americans get the most up-to-date vaccine, but the leftovers - more than 10 million of a record 110 million doses produced - will be destroyed before a new supply is guaranteed.

Ira Katz, a pharmacist certified to administer the flu vaccine, holds up his pharmacy's leftover supply of the vaccine, at Little Five Points Pharmacy Wednesday March 7, 2007, in Atlanta. [AP]

An Associated Press examination of this long-standing practice raises questions about its consequences. For years, policymakers have talked about letting doctors keep unused vaccine until new doses are in hand, donating leftover supplies to poor countries, or pushing back the expiration date. Wasted vaccine means lost money for drug companies and one stopped making flu shots because of it - setting the stage for a flu shot shortage in 2004.

Having no vaccine in the summer deprives travelers of the chance to get a shot before they visit places where flu is in season. It also prevents summer vaccinations for children, who need two doses the first time around.

"All of those issues have come up in the past," but there is a strong reluctance to change policy, said Dr. William Schaffner of Vanderbilt University, a government vaccine adviser. "These ideas clearly have merit and at the very least ought to be discussed."

The June 30 expiration date is set by the federal Food and Drug Administration and has less to do with the vaccine's shelf life than with the desire to tweak the recipe each year to include the three strains causing the most cases.

Manufacturers test throughout a flu season to ensure the vaccine stays potent, but they don't test beyond June 30 because it's assumed that new vaccine will be made, said Len Lavenda, spokesman for Sanofi-Aventis SA, which supplies most of the nation's flu shots.

However, vaccine degrades very slowly and not into anything harmful, said Dr. Peter Patriarca, a scientist who formerly worked for vaccine maker MedImmune Inc. and once headed the FDA's vaccine division. Patriarca says most vaccines would be stable for another year or two years, some as long as three or four.

The June 30 date is mostly to ensure that all old vaccine is gone before new doses come out.

"What they don't want to have happen is people inadvertently getting vaccinated with last year's vaccine," because it will not be as effective since it targets older strains, he said.

"There is some benefit to a system where unused vaccine is discarded even if it hasn't really lost that much potency," said Dr. John Treanor, a vaccine expert at the University of Rochester in New York.

Old vaccine could be a tough sell if one of the strains is not well-matched to what's expected to circulate. "You'd have to tell people next year that the vaccine they got could be inferior," said Dr. Walter Orenstein, a vaccine expert at Emory University.

One more argument for the current system: Straying from a set expiration date for an entire season's vaccine would probably cause a huge headache for those trying to manage vaccine supplies, and for manufacturers trying to calculate the following season's demand, added Dr. Carolyn Bridges of the federal Centers for Disease Control and Prevention.

But there also is risk in destroying old before new is available - the first shipments are usually by early fall.

After the 2002-03 season, Wyeth Pharmaceuticals had to destroy a third of the 20 million doses it produced because of low sales. The company lost about $35 million and then dropped out of the flu shot business. A national shortage followed in October 2004, when Chiron Corp. lost a manufacturing license that deprived the nation of half of its flu shot supply during the height of vaccination season.

Although there are more suppliers now than then, brewing vaccine takes six months at best and remains vulnerable to the vagaries of millions of chicken eggs and a fragile production system.

Stockpiling leftover vaccine until new vaccine is available "doesn't sound like an unreasonable thing to be doing," said another vaccine scientist, Dr. Robert Belshe at St. Louis University. After all, usually only one of the three vaccine strains changes - often, only slightly. Twice in the last decade, the recipe didn't change at all, said Alexander Klimov, a CDC flu strain expert.

And three times in the last decade, the vaccine strains recommended for the United States in one winter were identical to what was recommended for the Southern hemisphere the following summer, he said.

Also, several recent studies showed that even poorly matched vaccine can still be highly effective - something to consider amid worries about bird flu and efforts to stockpile vaccine to protect in a pandemic.

Dr. Stuart Brown, Georgia's director of public health, suggested a second wave of flu shots every spring and availability of one season's shot into the following summer.

"That would allow us to purchase just as much vaccine as we need and maybe a little more," he said, without worrying as much about losing money and tossing vaccine if deliveries don't arrive until November or later.

Georgia got less than half of its flu shot orders by Nov. 1 last year, and expects to have thousands of doses left this spring.

Despite a big 'Flu Shots Available' banner outside his Atlanta pharmacy, Ira Katz says few customers are interested this time of year and he's left with about 40 doses. "We're not at all hurting for vaccine, that's for sure," he said.

"This past year, the demand definitely was down," said Jean Ellis of the Visiting Nurse Associations of America. Many late-season orders were canceled, and lots of vaccine remains on shelves. Doctors and VNA clinics will get a refund of taxes paid but will still lose about $10 per dose. Losses of up to $20,000 a season have caused some clinics to quit offering shots.

As long as public demand falls short of supply and manufacturers can make enough fresh vaccine, "there doesn't appear to be any reason to hang on to it," said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases.

Even better, Fauci said, would be a universal, permanent flu vaccine effective for all strains of the virus, something his office has been researching.