Anne Schuchat, deputy director of the US Centers for Disease Control and Prevention (CDC), said 25 areas across the country -- among the 50 states and four main metropolitan areas identified in the CDC program -- placed their initial vaccine orders on Wednesday and will receive them by Tuesday.
"We are transitioning from the planning phase to the implementation phase," Schuchat told reporters on Thursday.
"This is really just the beginning."
The initial rollout, about two weeks earlier than expected, is welcome news to health experts who had expressed fears that the vaccine might arrive too late in the flu season to provide protection to the millions of Americans believed to be at risk.
The first doses will be in nasal spray form, safe for adults up to age 49 and for children two years and older, and the vaccine should be effective against A(H1N1) within eight days.
Schuchat expects that many of the first people receiving the vaccine will be health care workers on the front lines of the battle against a virus that has claimed more than 3,900 lives worldwide since it was uncovered in April.