"Vaccine availability is increasing steadily, but far too slowly," Frieden said. "It's frustrating to all of us. We are nowhere near where we thought we would be by now. We are not near where the vaccine manufacturers predicted we would be."
The vaccine that is available comes in both nasal mist and injectable forms. The first doses were only the nasal spray, called FluMist, designed for healthy people 2 to 49 years of age. But now, more than half the doses are injectable, he said.
While children continue to be particularly vulnerable to the disease, Freiden said, "we are seeing it increasingly affect young adults as well as children. We are still not seeing significant numbers of cases among the elderly, and that's characteristic of this virus."
That's also a marked difference from run-of-the-mill seasonal flu, which typically poses a much bigger threat to the elderly.
There is encouraging news, Frieden said. The genetic makeup of the H1N1 virus hasn't changed, meaning the swine flu vaccine and the antiviral drug Tamiflu are a good match.
Frieden said the H1N1 flu would probably occur in waves, but "we can't predict how high, how far or long the wave will go, or when the next will come."
"We are now in the second wave of pandemic influenza and whether this will continue through the fall into the winter, whether it will go away and come back in traditional flu season, only time will tell," he said.
To learn more about the H1N1 swine flu, visit the U.S. Department of Health and Human Services.
SOURCES: John Treanor, M.D., professor, medicine, and chief, infectious diseas
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