The Food and Drug Administration found serious problems of bacterial contamination at an influenza vaccine plant in England in 2003, 16 months before British regulators effectively closed the site and impounded its flu shots because of fears they were tainted.

Those earlier problems were among many revelations in about 100 pages of documents released yesterday by a House committee looking into how the United States lost about half this winter's flu vaccine supply just as the season for giving the shots began.

The documents, which include FDA inspection reports, letters and e-mails, also revealed that the agency was nine months late in giving Chiron Corp., the owner of the plant, a detailed report of the problems it found and then rebuffed the company's efforts to learn more about what it could do to fix things. At the same time, FDA managers overruled its inspection team and made its fixes voluntary rather than mandatory.

The new information appears to undercut the agency's assertions that it had no reason to suspect that past safety problems at the plant had persisted and might threaten its huge production capacity.

About 48 million doses of vaccine from Chiron's plant outside Liverpool were withheld from the U.S. market early last month after the British equivalent of the FDA denied the company a license to sell them.

The United States expected to have about 100 million doses of flu vaccine this winter. Instead there will be 61 million doses, with some not arriving until January. The shortage has caused widespread public anxiety and has forced health departments nationwide to laboriously reallocate vaccine after much of it already had been distributed.

Yesterday's revelations drew distinctly partisan responses at a congressional hearing.

"FDA's laxity has had a heavy cost. If FDA had ensured that the problems identified in June 2003 were fixed, this year's flu crisis might never have happened," said Rep. Henry A. Waxman (Calif.), the ranking Democrat on the House Government Reform Committee.

In contrast, Rep. Thomas M. Davis III (R-Va.), the chairman, twice elicited from acting FDA Commissioner Lester M. Crawford statements that no protocols had been violated in the agency's response to the problems at the Liverpool plant, which has had three owners in the past decade.

"If protocols need to be tweaked, then let's talk about tweaking them," Davis said.

Despite the revelation of problems dating at least to 2001, Crawford testified that except for the late delivery of its full report on the agency's June 2003 inspection, the FDA has done nothing wrong -- and it would do nothing differently if given the chance.

Specifically, he defended the decision not to send inspectors into the plant for 16 months after the 2003 visit (which found deficiencies in 20 production activities), arguing that regular telephone conference calls and other communications were a form of "re-inspection."

Furthermore, he told the committee there was "no connection" between the 2003 deficiencies and the ones that led British regulators to prohibit sale of the 2004 vaccine production, even though the contamination found this year involved the same serratia bacteria found in unfinished samples of vaccine in the past. When they did revisit the Liverpool plant last month, the agency's own inspectors reported that at least three possible sources of contamination were "not corrected from previous inspection of 2003," according to one of the documents.

The FDA chief told the committee several times that the fact that the plant's 2003 vaccine ultimately tested pure and was released for sale was evidence Chiron had fixed the earlier problems.

Some experts have said that if the problems at the Liverpool plant had been recognized earlier, American public health officials might have been able to seek other sources of influenza vaccine on the world market. But in response to a question from Rep. Christopher Shays (R-Conn.) about whether knowledge of the problems five months earlier would have made a difference, Crawford said: "We couldn't have done anything about it."

The events that led to the loss of Chiron's vaccine began on Aug. 25, when the company told the FDA that it had found bacterial contaminants in some of its finished vaccine. The Medicines and Healthcare Products Regulatory Agency (MHRA) -- Britain's FDA -- was notified at the same time.

Twice in the next month, on Sept. 13 and 28, MHRA sent representatives to the plant for multi-day inspections and data-gathering sessions. Except for a brief visit with an FDA official who was, by chance, in the plant on Aug. 25 on another matter, the FDA dealt with Chiron entirely from a distance, through letters, e-mails and telephone calls.

The FDA was apparently unaware of the more intensive response by MHRA because the British agency is forbidden by law from communicating with its U.S. counterpart without receiving permission from the company being inspected -- in this case, Chiron.

MHRA revoked Chiron's license to sell flu vaccine on Oct. 5, based on a report by its own inspectors and an internal investigation the company conducted into the contamination. For reasons that were not immediately clear yesterday, the FDA did not receive a copy of the company's report until after the British took action.

In response to a series of questions shouted at Crawford by Rep. Elijah E. Cummings (D-Md.), the agency official said: "FDA is not perfect. . . . We got the full report on October 5 and made the determination that this vaccine was not usable. . . . It never got on the market."

The one FDA action he said was a mistake was the agency's failure to send its full report on the June 2003 inspection to Chiron in September 2003. That was when the FDA decided to make its improvements voluntary, not mandatory. Chiron requested and received the full report in June 2004.

The company had asked for a meeting with FDA officials after the 2003 inspection, but the agency never granted one, apparently because it did not view it as necessary.

CDC Director Julie L. Gerberding and Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases, testify on the flu vaccine shortage.