There is no vaccine yet against the swine flu virus, but Bruce Gellin, director of the National Vaccine Program Office at the Department of Health and Human Services, says the first doses of one could be ready by early September.

Gellin says they are still studying the virus to learn more about it.

"There's a lot that we don't know about this and until we know more we won't know whether or not what we're seeing now will stop where it is in the sense of just becoming like a seasonal virus, whether it's a pandemic but mild as we've experienced in the past or a severe pandemic as we experienced at the beginning of the century," he says.

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