WASHINGTON - The Food and Drug Administration is unlikely to clear influenza vaccine made by Chiron Corp. as safe for Americans to use this flu season, Dr. Lester M. Crawford, the agency´s acting commissioner, said Friday. It was unclear whether the lack of vaccine might lead to more flu deaths this year. 

Crawford and Dr. Julie Gerberding, head of the Centers for Disease Control, sidestepped such questions at a House Government Reform Committee hearing. In a typical year, an estimated 36,000 Americans die of the flu.

Dr. Jim Young, president of research and development at MedImmune, which makes an alternate flu treatment available to a limited population of healthy people, testified that any spike in the death toll largely hinges on whether scarce flu vaccine makes its way to those most at risk. They include those with impaired immune systems, such as the very young, the elderly and people with medical conditions.

The CDC was asking healthy adults to forgo flu shots or to use MedImmune´s FluMist if they磖e within the 5- to 49-year-old age range for that product, Gerberding testified. But as she spoke, Young later testified, the National Institutes of Health was advising employees in its hospitals not to take FluMist.

"The agencies are putting out mixed messages," Young complained.

Crawford´s pessimism about the Chiron vaccine came as FDA officials in England met with Chiron officials and were poised to begin an in-depth inspection of the company´s Liverpool vaccine production facility on Saturday and Sunday.

Asked if the FDA was likely to coax free 40 million impounded doses of flu vaccine that Chiron testing indicated were free of contamination with bacteria, Crawford said, "It´s not possible to say if any of them are salvageable at this point. I have to present to you a pessimistic point of view."

Crawford told reporters afterward that the FDA probably would have made the same decision as its British counterparts to suspend Chiron´s vaccine production and exports. The British decision, announced Tuesday, halved the U.S. flu vaccine supply.

Chiron had alerted all regulators Aug. 25 that it had detected eight lots of flu vaccine contaminated with a bacteria that can grow in vaccine and, in vulnerable humans, can cause urinary tract infections. U.S. officials expected that would mean as little as a 10 percent drop in this year´s flu vaccine supply, or 4 million to 8 million doses.

Chiron had traced the bacterial contamination in those eight lots back to two bulk lots of viral antigens. The final vaccine contains three different inactivated viral antigens to protect people against the season´s dominant flu strains. The contaminated bulk lots were the influenza B strain, said Dr. Karen Midthun, deputy director for medicine at the FDA´s Center for Biologics.

The British version of the FDA met with Chiron last Friday. Meetings Monday in England continued well into the night, Crawford testified, leading to Tuesday morning´s announcement.

Gerberding told the House hearing that the head of Chiron awakened her Tuesday to alert her to the British license suspension. The FDA´s weekly conference call with Chiron, covering the company´s final report on the contamination was due to happen later Tuesday.

U.S. health officials were stunned by the British action, since the FDA´s monitoring had suggested most of Chiron´s vaccine would be fine. FDA staffers said the agency would have received Chiron´s most detailed report on the contamination question in the conference call pre-empted by Tuesday´s license suspension.

By Friday, Crawford was telling reporters, "We would have probably made the same decision."

Much of Friday´s discussion underscored the frailty of the nation´s supply of indispensable vaccine and the scant number of manufacturers producing it.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said manufacturers can make higher profits with blockbuster drugs that patients take regularly. He said a year´s supply of Lipitor costs $1,608 vs. $3,500 for Viagra. The price of a year´s supply of flu vaccine: $7 to $10.

"We need to help with incentives," Fauci told the committee.