United States now expects to receive the first batch of swine flu vaccine in early October, a few weeks earlier than expected, says Health Secretary Kathleen Sebelius.
"We're on track to have an ample supply by October," Sebelius told ABC television "but we may have some early vaccine as early as the first full week in October."
Pharmaceutical firms have been racing to produce the vaccine in time for the start of the northern hemisphere's winter flu season, with the US government aiming for the first batch of the H1N1 shot to be made available by mid-October.
"The first week in October, we expect some of the vaccine to begin to roll," Sebelius said.
News of the accelerated delivery of the vaccine is a boost to Americans worried about an imminent spike in swine flu cases.
Health experts 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.
"We'll get the vaccine out the door, the earliest doses are probably going to be targeted to health care workers and other high-priority groups," Sebelius said.
On Friday, the health secretary said clinical trails had shown a single dose of the vaccine was enough to ensure immunity within 10 days.