There was cautious optimism today about the rush to get a swine flu vaccine ready for the fall flu season.
"We are on track in development," said Dr. Marie-Paule Kieny, director of the World Health Organization's initiative for vaccine research.
But questions persisted about whether there will be enough doses to go around and whether they'll be safe.
Watch "World News With Charles Gibson" tonight at 6:30 ET for the full report
Kieny stopped short of predicting how much vaccine would be...Full Story