Companies that make flu vaccines can “borrow” U.S. government supplies of the shots to redistribute under a new federal plan to deal with an initial immunization shortage, officials said on Thursday.

The Centers for Disease Control and Prevention said it was still struggling to make up for the chaos caused by the loss of half the anticipated national vaccine supply when maker Chiron Corp. lost its license at the beginning of flu season last October.

“We’re pulling out all the stops and doing everything we can to see that those who need vaccine most get it,” CDC Director Dr. Julie Gerberding told a telephone news briefing.

“Influenza season has not peaked and people can still benefit from vaccination.”

While lines formed early in the season as people most at risk from flu rushed to get vaccine, news of the shortage discouraged many, who gave up trying.

Now, many regions have reported flu vaccine is going unclaimed. The CDC fears if doses of vaccine go unused, more people will catch the flu and manufacturers will be reluctant to make more doses for next year.

Gerberding said the CDC was taking some unusual steps to get the vaccine from glutted areas to areas still seeing shortages.

“CDC is immediately making available the remaining 3.1 million doses of influenza vaccine in the federal government’s emergency reserve to Sanofi Pasteur (SASY.PA) (formerly Aventis Pasteur (AVEP.PA)), which, in turn will market and sell the vaccine to public and private providers,” the CDC said in a statement.

“This strategy would allow providers to order vaccine directly from Sanofi Pasteur or a vaccine distributor, rather than working through state or local health departments.”

Providers could return unused vaccine for a refund.

Leftover doses from the federal Vaccines for Children program, which provides for uninsured children, would also be made available, Gerberding said.

Gerberding said the CDC was looking at long-term ways to ensure a more predictable supply of vaccine. She and other officials have stressed for years that the United States is vulnerable because only three companies supply influenza vaccine to the U.S. market.

At least 20 states have lifted all restrictions on who can get flu vaccine. The CDC always struggles to persuade Americans to get vaccinated against influenza, which kills 36,000 people in an average year and puts 200,000 into the hospital.