Just about everyone at a hastily called congressional hearing on America's vanishing flu shots agreed yesterday that the nation's current vaccine supply system is broken. The possible fixes offered by experts, however, appear to be difficult, uncertain and many years into the future.

Among the suggestions made to members of the House Committee on Government Reform were unspecified financial incentives to lure more drug companies to enter the high-headache, low-profit vaccine field; lessening those companies' exposure to lawsuits from consumers; increasing public recognition of the value of vaccines; and having policies to promote greater vaccination of people at low risk.

"We continue to have a completely fragile vaccine production system in this country -- and it is getting more fragile every day," Julie L. Gerberding, director of the Centers for Disease Control and Prevention, told the committee.

Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases, said a Bethesda pharmacist gave him data yesterday morning that Fauci said help explain why drug companies prefer to put their money into the search for blockbuster drugs that people take repeatedly, rather than into making vaccines that are taken at most once a year.

"A year's supply of Lipitor to lower cholesterol is $1,608. A year's supply of 50-milligram Viagra is $3,500. He told me the Aventis Pasteur [flu] vaccine generally sells for $7 to $10," Fauci testified. "We need help on incentives."

Both Fauci and Gerberding said they were awakened before dawn on Tuesday by telephone calls from an executive at Chiron Corp., who said the company would not be able to deliver an expected 48 million doses of influenza vaccine this fall. That was about half the supply health officials were counting on.

Since then, U.S. officials said they have worked virtually nonstop to come up with a strategy for directing the diminished supply of vaccine to high-risk populations only.

Ironically, one of the best ways to help ensure that this situation will not occur again is to urge more people to get flu shots in the future, an executive of one company said.

"A universal recommendation that all Americans receive annual flu vaccine will drive demand . . . which will, in turn, provide the impetus on the part of vaccine manufacturers to increase their production," James Young of MedImmune, a biotechnology company in Gaithersburg, said.

MedImmune makes FluMist, a "live virus" vaccine that is squirted into the nose rather than injected into the arm, as is the case with traditional "killed" flu vaccine.

The company has the capacity to make 20 million doses but made only 2 million this year because its product sold poorly last year in its first year on the market, and the company ended up throwing away about 5 million doses. FluMist can be given only to healthy people age 5 to 49, which rules out most people at highest risk for influenza complications.

Young said that after what he called the "very disappointing and sobering experience" last flu season, the company considered getting out of the flu vaccine business, as did its partner in developing FluMist, the pharmaceutical giant Wyeth.

MedImmune decided to stay in the business, however, and is expanding capacity to be able to make 40 million to 50 million doses a year, he said. The company also hopes to get permission from the FDA to market FluMist to a broader segment of the population.

Young said the trend for U.S. pharmaceutical companies to build plants overseas increases the nation's vulnerability, because if there is "a catastrophic event or the emergence of a new pandemic [influenza] strain, the host country may embargo vaccine for use within its borders."

Christine Grant, a vice president at Aventis Pasteur, which makes injectable flu vaccine at a plant in Pennsylvania, warned that it takes "five to seven years" to build a vaccine factory and get it inspected and licensed for use. This is because of the "inherent complexity" of producing biological products such as vaccines, in contrast to drugs, most of which are inert chemical compounds, she said.

Scientists at Aventis, like researchers elsewhere, are working on ways to grow the flu vaccine virus in cell cultures rather than in the traditional and messier system of using fertilized chicken eggs. The new technique, however, may not markedly speed the turn-around time for producing flu vaccine.

"The virus doesn't grow any faster" in cell culture, Grant said. "It may grow more uniformly and predictably, at best."

If a deadly pandemic flu strain appears, it will take four to six months before a usable vaccine comes out of manufacturing plants, she said after the hearing.

Several lawmakers blamed fear of lawsuits for the diminished vaccine production capacity.

"You know, we don't even make ladders in the United States," said Rep. John L. Mica (R-Fla.). "Vaccines and ladders. Why? Because of the field day we've created for trial attorneys. I'm pretty bitter about it."

Julie L. Gerberding and Anthony S. Fauci, center, confer with Lester M. Crawford, acting commissioner of the Food and Drug Administration.