Oct. 24, 2009 (United Press International) -- Manufacturing difficulties are delaying the delivery of vaccines for the H1N1 flu strain, with less than half of the total shipped so far, U.S. officials say.

The federal Centers for Disease Control and Prevention said Friday that 16.1 million doses of H1N1 vaccine out of an expected total of 28 million to 30 million doses had been shipped to warehouses, the Wall Street Journal reported.

"We are nowhere near where we thought we'd be by now," CDC Director Thomas Frieden told the newspaper. "We share the frustration of people who have waited in line or called a number or checked a Web site and haven't been able to find a place to get vaccinated."

Frieden wouldn't give specific projections for delivery of more doses, but did indicate he expected the supply to be "much more widespread" within the next several weeks.

Manufacturers such as Glaxo and Novartis (NYSE:NVS) are reportedly encountering delays. Glaxo, expected to provide 7.6 million U.S. doses of vaccine, has yet to gain regulatory approval and Novartis, set to make 90 million doses, is seeing low yields from its "seed" virus, the Journal said.