So far, more than 128 million doses of flu vaccine have been distributed, Hamburg said, but not all the doses have been administered to people yet.
She said that people who already have the flu may also be experiencing local shortages of Tamiflu.
"We do anticipate intermittent, temporary shortages of the oral suspension form of Tamiflu -- the liquid version often prescribed for children -- for the remainder of the flu season. However, FDA is working with the manufacturer to increase supply," she said.
Flu season typically peaks in January or February but can extend as late as May. This flu season is turning out to be more severe than last year's.
Officials at the U.S. Centers for Disease Control and Prevention said on Friday that 47 states were reporting widespread influenza activity, although flu case numbers were beginning to subside in some regions, especially in the Southeast, where the flu showed up first.
It's still not too late to get a flu shot to help protect yourself, Hamburg stressed. She noted that it takes about two weeks after vaccination for your body to develop an immune response to provide protection against the flu.
People who want to get vaccinated can visit flu.gov, click on the "Flu Vaccine Finder," enter their zip code and find a list of clinics, supermarkets, pharmacies and other flu vaccination locations in their neighborhoods.
But before you go to one of the locations, call ahead to confirm that they have the flu vaccine, Hamburg advised.
According to recommendations from the CDC, all adults and children who are at least 6 months old should receive a flu vaccination each year. The best time to get vaccinated is in the fall.
The U.S. Centers for Disease Control and Prevention has more about the flu and flu vaccine.
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