By Elizabeth Landau
CNN

ATLANTA — Questions abound about how to best inoculate the world against swine flu as health officials plan for a campaign that could dwarf any previous flu vaccination effort.

Among the issues to be resolved are the amount of vaccine likely to be available, the timing of the vaccine's availability, how it would be distributed, who would provide the shots, who would pay for them and whether it will be possible to track potential side effects.

At a recent meeting at the Centers for Disease Control and Prevention, health officials said U.S. demand could reach 600 million doses of vaccine, enough for two doses for each of the approximate 300 million people in the United States. That's in case two doses are required for children and adults under 50, CDC representatives said.

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