Hurricane evacuees living in crowded shelters and people at high risk of influenza complications should get priority for flu vaccines over the next six weeks, U.S. health officials said on Wednesday.

“We know those shelters could be a place where respiratory illnesses can easily spread, and if there is any population that deserves first access to the vaccine, it’s the people who have already gone through so much difficulty,” Centers for Disease Control and Prevention Director Julie Gerberding said at a news conference.

Along with Katrina evacuees in shelters, officials are concerned about people age 65 and older or with weak immune systems, children aged six months to 23 months and pregnant women - the groups most likely to become seriously ill or die from the flu.

Government health officials and leaders of medical organizations united in calling on doctors to give flu shots only to those groups, as well as to health-care workers or others who come in contact with them, until October 24.

“We’re asking those who provide influenza to give the first available doses to people in our priority groups ... Getting an influenza vaccine is the best way to protect yourself and your patients against this disease,” Gerberding said.

French company Sanofi-Aventis has donated 200,000 doses of flu shots for hurricane victims. The doses are on their way to health departments in areas that are housing hurricane evacuees, Gerberding said.

Others who want the vaccine can get it after October 24, officials said, as long as the supply lasts.

The CDC estimates 180 million Americans should get a flu shot every year but fewer than half that number do.

Last year, vaccine maker Chiron Corp. lost its manufacturing license because of contamination at a British plant, and half the anticipated U.S. supply was lost. Long lines formed to get vaccine and health officials scrambled to get about 60 million doses from other suppliers.

U.S. officials expect between 71 million and 97 million doses to be available for the upcoming flu season, depending on how much Chiron can provide. Flu season typically starts in December and runs through March.

Three million of the doses will be MedImmune Inc.‘s Flumist nasal spray vaccine, which can be given to healthy people ages five to 49 who are not pregnant.

Influenza kills an estimated 36,000 Americans and puts 200,000 in the hospital in an average year. Because the virus constantly changes, the vaccine must be reformulated and made fresh every year in a process that takes months.