U.S. sees 10 million more H1N1 vaccine doses next week

President Barack Obama on Friday expressed frustration about the slow pace of production of the vaccine, which has resulted in just 26.6 million doses as of Friday, far below earlier estimates of 40 million by the end of October.

Sebelius said those initial estimates were based on "overly optimistic" predictions by the five contracted vaccine makers for the U.S. market -- MedImmune, a unit of AstraZeneca, Sanofi-Aventis, Australia's CSL, GlaxoSmithKline and Novartis.

But production was now increasing and vaccine doses were being shipped seven days a week, Sebelius told CNN.

"The good news is that we have, as of yesterday, 26.6 million doses out and around the country. We are expecting another 10 million doses next week," Sebelius said. "So the vaccine is beginning to roll in larger volumes. And it's being distributed as quickly as it comes off the line."

"It's being shipped overnight. We're getting it from producers seven days a week," she added.