ATLANTA (AP) -- A potential fall swine flu immunization campaign may involve an unprecedented 600 million doses of vaccine, but health officials are still trying to figure out how to find enough workers to administer all those shots.

Officials are also looking at how to keep track of side effects if it's given at the same time as the seasonal vaccine. That could make it difficult to figure out which vaccine was causing the side effects.

At a Friday meeting of a national vaccine advisory committee, officials said the swine flu campaign could far eclipse the roughly 115 million doses of seasonal flu vaccine and the 150 million doses of childhood vaccines distributed each year.

However, officials haven't decided whether all Americans would get immunizations or whether the vaccination campaign will take place.

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