Dr. Tom Frieden, director of the Centers for Disease Control and Prevention in Atlanta, said there are reports of spot shortages of flu vaccine.
"Some people haven't been able to find vaccine and I understand that they're frustrated," Frieden told reporters during a telephone news conference. "Some providers haven't been able to get vaccine for their patients and they're also frustrated and that's understandable."
As this week, about 129 million doses of the seasonal flu vaccine had been distributed and that means there is more vaccine out there for providers to order, he said.
"There are some formulations of vaccine that may be out of stock while it gets into the system. Particularly for younger children," Frieden said. "Providers who want to order more influenza vaccine can visit the influenza vaccine availability tracking system -- IVATS -- and you can find that at www.preventinfluenza.org/ivats."
Providers who have exhausted their vaccine or patients who want to find vaccine can go on to the web site flu.gov.
"You can put in your ZIP code and find out where there's flu vaccine in your area. If you want to double check, you might call before going. But that's being kept up-to-date," Frieden said.
"I want to remind everyone that although the flu vaccine is far from perfect, it's by far the best tool we have to prevent influenza. You can still protect yourself through vaccination. Particularly for folks out West. You probably have most of the flu season still to come."