The program has been plagued with problems and information gaps:

Health officials have been terrible at predicting when and how much vaccine would be available. Only about 44 million doses have been shipped so far. At first, officials said more than three times that would be out by now.

At times vaccine shipments have been inexplicably lopsided. For example, smaller counties in Illinois and California have received the same amount delivered to counties with seven times as many people.

Health officials have stressed that people most at risk for swine flu complications should go to the head of the line, but they haven't tried to make sure that actually happened.

And despite pledges that they would be transparent about the vaccine program, some health officials have refused to disclose where all the doses are going, and they have held back on public-service announcements telling people who should be coming in for shots.

To be fair, health officials say, the government deserves credit for a herculean effort to develop and distribute a safe and effective vaccine against a deadly virus that was first identified only seven months ago.

"You have a brand-new disease that gets identified in April. By October, you have a vaccine for it. By any standards, it's a miracle," said Diane Helentjaris, director of the Virginia Department of Health office handling swine flu response.

But complaints have been mounting, with lawmakers this week holding hearings in Washington and elsewhere, pressing for explanations.

"Calls are still coming in to me about, 'Why can't I get the vaccine?' " said Andrea Stillman, a Connecticut state senator speaking at a hearing Wednesday in Hartford.

She noted reports of places where vulnerable patients can't get the vaccine.

"Obviously we're very frustrated in southeastern Connecticut," she said.

People are frustrated everywhere, said Sen. Susan Collins (R., Maine). At a hearing in Washington on Tuesday, she complained of "layers of misinformation and miscommunication."

Arthur Caplan, director of the University of Pennsylvania's Center for Bioethics, said health officials should have done more to make sure limited doses get to the people most at danger from the virus. And he said they should have been tougher on nurses and other health-care workers who are putting their patients at risk because they declined to get a shot.

"It is not working right at all," Caplan said.

In their defense, officials at the Centers for Disease Control and Prevention have said that the main issue is insufficient vaccine from manufacturers - something CDC cannot control - and that health authorities are doing the best they can.