When it comes to getting flu shots for its citizens, the United States may someday soon look like a giant version of Canada, its national-health-plan neighbor to the north.

Like the United States, Canada has only two suppliers of influenza vaccine, fluctuating public enthusiasm for flu shots and a lot of wasted doses. What it doesn’t have is any question about who pays for uncertainty or miscalculation. It is the government.

Canada’s public works ministry orders about 90 percent of the influenza vaccine the country uses each year. The Ottawa office tells vaccine manufacturers how much to make, based on the share of the national total the firms have won by bidding on long-term contracts.

The companies make extra doses. This “on-spec’’ production is sold in the small private market operating outside Canada’s national health system, or on the world market. But the bulk of vaccine is made without financial risk.

The United States appears headed toward such an arrangement.

Many experts believe that this season’s vaccine calamity - half the nation’s supply evaporated overnight on Oct. 5 - is proof that the government needs to be more involved in ensuring a stable supply.

Secretary Tommy Thompson was asked whether he favors the federal government guaranteeing a market for a specified number of doses of flu vaccine each year. “Yes, I do,’’ he said, without elaborating.

An assured market would mean that vaccine makers would no longer face discarding and not being paid for 10 percent to 20 percent of their yearly production for the United States. That occurred in the 1990s when several companies quit, leaving Aventis Pasteur and Chiron Corp. the only makers of injectable vaccine for the United States.

A guaranteed market would not have prevented this season’s scarcity of flu shots, which occurred when British regulators impounded 48 million Chiron doses because of bacterial contamination. What it might do, though, is lure other vaccine companies back into the U.S. market, making the supply more secure.

The flu shot is a combination of three vaccines, each to a different strain of influenza virus. It takes six months to produce, is sold for three months and cannot be used in the next flu season because the viral recipe changes annually.

The Canadian system is as fragile as the American in one sense. It is also dependent on only two vaccine producers - Aventis Pasteur and ID Biomedical. But with a total production of 9.7 million doses this year - compared with 100 million anticipated for the United States - Canada would never face a problem the magnitude of that of the United States.

ID Biomedical, which has its headquarters in British Columbia but makes vaccine in Quebec, has a contract to fill 75 percent of Canada’s order. This year, that is 7 million to 8 million doses. The company made 500,000 for the private market.

ID Biomedical has an additional 1.2 million doses “that are still available,’’ a spokeswoman, Michele Roy, said last week. Although the vaccine is not licensed for use in the United States, the Food and Drug Administration might allow it in as an “investigational drug,’’ the agency’s acting director, Lester Crawford, has said.