Don't expect imports of flu shots from Canada or other countries to ease the crippling shortage, the nation's health secretary cautioned Thursday.

The Food and Drug Administration (search) is in discussions with two companies that sell flu vaccine (search) in Canada and elsewhere, and have found a few million unsold doses.

But that vaccine is not licensed for sale in the United States, and thus meeting FDA requirements in time for this flu season "is doubtful," Health and Human Services Secretary Tommy Thompson told reporters Thursday.

"The only way," Thompson said, is if foreign supplies met certain conditions that might allow some to be offered as experimental vaccine. But even that determination could take too long to help.

"It doesn't look promising," he said.

Thompson's comments came after President Bush suggested during Wednesday's presidential debate that Canadian supplies might ease the vaccine shortage. "We're working with Canada to hopefully ... help us realize the vaccine necessary to make sure our citizens have got flu vaccinations during this upcoming season," Bush said.

The president made those comments even though his administration has fought municipalities' efforts to import cheaper medications from Canada, questioning the drugs' safety.

Also Thursday, Thompson sent a letter to the attorney general of every state urging aggressive prosecution of vaccine price-gouging. Hospitals around the country have reported distributors offering vaccine for as much as $100 a shot. Retail, flu shots usually cost $12 to $20. Federal health officials are sharing such reports with state prosecutors, Thompson said.

"Thoroughly investigate reports of price-gouging and prosecute those engaging in this immoral and illegal activity to the full extent of the law," Thompson urged the attorneys general.

The vaccine crisis began last week when British regulators shut down shipments from Chiron Corp., which had made 48 million flu shots in an English factory that were destined for the United States. Some batches of the vaccine were contaminated with a worrisome bacteria.

The surprise decision cut the U.S. supply of flu shots almost in half. The government is urging healthy adults to skip the shot this year so the remaining 55.4 million doses can go to the youngest, oldest and sickest Americans, who are most vulnerable to influenza (search).

FDA inspectors still are in England trying to determine how serious the contamination problem is, and whether every batch of Chiron vaccine is affected. Thompson expects a final report early next week.

Thompson said the bigger issue is how to increase the number of vaccine makers willing to sell in this country so future shortages are averted. He urged Congress to authorize the government to purchase up to 100 million doses of flu vaccine each year, to guarantee companies enough of a market "that we have a ready source of vaccine year after year."

Vaccines seldom are profitable, particularly flu vaccine, which is good only for the year in which it's made. Most years, a few million doses go unsold and are thrown away.