The legal experts said they were surprised at how swiftly the Justice Department started looking into Chiron, just one week after the company announced that it could not supply the vaccine.
"Prosecutors are becoming a lot more aggressive at the federal level," said Jamie Wareham, a partner at Paul Hastings. "They don't want to look like they've been blindsided by the Eliot Spitzers of the world," he added, referring to the New York state attorney general who led high-profile litigation against brokerage firms.
Meanwhile, throughout the nation, healthcare providers remained worried about the outlook for the flu season and awaited details about specific allocation decisions.
Denise Ratcliffe, chief operating officer for Christian Health Care Center, which has about 600 patients in its nursing home in Wyckoff, N.J., said the shutdown of Chiron's production had cost her facility its entire allotment of 1,300 shots.
"Virtually all of the long-term facilities in New Jersey had contracted with Chiron," Ratcliffe said, adding that there were "big questions" about the details of reallocation and how the priority for vulnerable populations would be carried out.
CDC officials said states that had relied on Chiron for all of their flu shots this year would get priority, but the names of those states weren't released.
The California Department of Health Services has received only about a quarter of the vaccine it ordered from Aventis and none from Chiron. State officials said they were working overtime trying to get what remained of the vaccine to the most needy.
"We're not quite sure how it's going to work out," said Robert Miller, a spokesman for the department. "We're having a lot of meetings and conference calls" with the CDC.
CDC officials urged at-risk patients to see doctors if they developed flu-like symptoms so they could receive medicine, if necessary. Gerberding said the CDC was stockpiling Tamiflu and Flumadine, drugs that treat the flu if taken in the early stages of infection.
Chiron's shares closed Tuesday at $33.74, down 51 cents, on Nasdaq.
Times staff writers Emma Schwartz, Julie Tamaki, Marc Lifsher and David Pierson contributed to this report.