Monday Kathleen Sebelius, Health and Human Services Secretary, said 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 Monday 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 a thousand 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, The Associated Press reports.
Two days after the H1N1 flu was declared a national emergency, vaccine shortages around the country are creating anxiety and concern.
In Baltimore, resident Ivette Brown expressed her frustration with the system.
"We've been turned away, we were told they don't have anything," Brown told ABC News. "My children's health is at stake," ABC News reports.
Anne Schuchat of the U.S. Centers for Disease Control, speaking on CNN, advised healthy adults over 25 and senior citizens to wait and allow more vulnerable patients -- children, young adults, healthcare workers, pregnant women, adults with chronic conditions and parents and others who take care of infants -- to receive the vaccine first.
President Barack Obama has declared 2009 H1N1 swine flu a national emergency which the White House said will make it easier for U.S. medical facilities to handle a surge in flu patients by allowing the waiver of some requirements of Medicare, Medicaid and other federal health insurance programs as needed, Reuters reports.