WASHINGTON — Health and Human Services Secretary Kathleen Sebelius said today the swine flu vaccine "is coming out the door as fast as it comes off the production line."

But at the same time, she acknowledged delays in getting a sufficient supply for all those demanding it.

"We were relying on the manufacturers to give us their numbers, and as soon as we got numbers, we put them out to the public. It does appear now that those numbers were overly rosy," Sebelius said in one interview. "We do have a vaccine that works," she said. Sebelius said the immune response is working faster than officials anticipated.

Appearing this morning on nationally broadcast news shows, she said officials now have a supply of about 16.5 million doses of the vaccine, while conceding that's millions of doses below the amount needed.

Sebelius said she couldn't predict just how widespread the virus will be. Roughly 1,000 people have died from it so far in the United States. But she also said officials do not believe there is yet any cause to close down schools and cease other daily activities.

President Barack Obama declared a health emergency over the weekend to give hospitals and health professionals more leeway from federal regulations to respond to the illness.