(AP) -- A U.S. health official said a swine flu vaccine could be available as early as October, but only if vaccine production and testing run smoothly this summer.

Dr. Anne Schuchat (Shook-it) of the U.S. said the agency began shipping virus samples to manufacturers in the past several days. The government will have to review the safety and effectiveness of what's produced, and decide if a vaccination campaign is warranted. October is about the time seasonal campaigns generally get rolling.

CDC officials reported more than 8,500 probable and confirmed cases in the U.S., including 12 deaths and more than 500 hospitalizations.

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