The elderly, young children and those with chronic health conditions who are the most vulnerable to flu complications need the shots more.

``This is going to be a shortage year,'' said Florida Health Secretary John Agwunobi.

``We have to assure that we maximize whatever vaccine supply we can lay our hands on.''

Up to half of this year's expected flu shot doses for the United States became unavailable Tuesday when Britain shut down the plant of California-based vaccine maker Chiron Corp. because of manufacturing problems.

The announcement left state health officials, doctors and clinics scrambling to devise a solution.

Chiron is one of two companies that makes flu shots for the U.S. market and was supposed to provide about 46 million to 48 million doses. The rest of the nation's supply, roughly 54 million flu shots, is coming from French provider Aventis Pasteur, the world's leading supplier.

The Florida Department of Health ordered about 300,000 doses - nearly all of its expected supply - from Chiron. As a result, only a small number of public health clinics have vaccine, Agwunobi said.

But 130,000 flu vaccines made for children should be available because they were ordered from Aventis Pasteur, he said.

Private providers, including hospitals, doctors offices and seasonal flu shot clinics, supply most vaccines in Florida.

County health clinics give 10 percent to 20 percent of flu vaccines each year.

Florida had an average flu season last year, although flu fears sparked a run on vaccines. There is no way to predict how hard the state will be hit this year, Agwunobi said. Florida's flu season typically peaks in February or March, later than other parts of the country.

On Tuesday, Maxim Health Systems, a company that sets up flu shot clinics in groceries and drugstores, was waiting for recommendations from the Centers for Disease Control and Prevention before deciding whether any changes will be necessary, company spokeswoman Jill Totenberg said.

Some businesses that ordered vaccine supplies from Aventis Pasteur do not know whether they will receive future shipments.

``The flu shot scarcity is the only thing anyone is talking about today,'' said Doctor's Walk-In Clinic medical director Stephen Dickey.

Dickey ordered 17,000 doses for Doctor's Walk-In clinics in Hillsborough and Pinellas counties from Aventis Pasteur. He received 2,000 last week.

He was expecting a shipment of 3,000 doses today but was told by representatives from Aventis Pasteur that ``we can't guarantee anymore after that.''

The shortage comes during the first year that the Centers for Disease Control has widened recommendations to include infants and toddlers as being in high-risk groups of flu complications.

The federal health agency now recommends that children between 6 and 36 months get flu shots because they are at higher risk of developing complications.

Elderly adults and those with chronic health conditions are also considered to be high risk, according to the CDC.

Pediatric Health Alliance offices in Hillsborough and Pinellas counties have pushed to get flu vaccinations for young patients who have diabetes and asthma, immunization director Patricia Jeansonne said.

But there may not be enough for all babies and toddlers, who are supposed to receive two doses the first year they are vaccinated, Jeansonne said.

Because of this year's hurricanes, Pediatric Health Alliance lost 10 percent of its 6,000 doses when their offices lost refrigeration after power outages.

On Tuesday, Health Alliance staff were looking for alternate clinics - such as in groceries - to recommend to parents who might seek flu shots for their healthy children.

The Florida Health Department will draft recommendations this week for private providers on which patients should be first in line for shots.

The United States had a supply of about 90 million doses of vaccine last year and should expect about 56 million this year.

``There's still a fair amount out there,'' Agwunobi said.

For a flu shot clinic locator guide, visit the American Lung Association at

For a flu shot clinic locator guide, visit the American Lung Association at www.lung usa.org. usa.org.

Information from The Associated Press was used in this report. Reporter Susan Hemmingway Johnson can be reached at (813) 259-7951.