Companies that provide flu- shot clinics at businesses for employees are canceling due to a vaccine shortage and pleas from health agencies to save doses for the medically vulnerable.

Meanwhile, at grocery and drugstore clinics that began Oct. 1, patients are being asked whether they fall into high-risk groups.

Anyone over age 65 is considered at high risk from complications if they were to catch the flu, according to the Centers for Disease Control and Prevention.

So are younger adults and children with chronic health conditions, pregnant women, and babies and toddlers between 6 and 23 months.

``We did a lot of corporations ... but as of this morning, no more,'' said Maxim Health Systems wellness services director Steve Wright on Wednesday.

The Maryland-based company will follow the CDC's recommendations, since most businesses employ workers younger than 65, he said.

Maxim also provides seasonal clinics at Publix, Kash 'n Karry, Walgreens and Albertsons stores. Its nurses on Wednesday started asking potential patients to fill out questionnaires about risk factors, Wright said. Those not considered high-risk will not be vaccinated by Maxim.

This year's vaccine shortage is due to the U.S. supply being cut nearly in half on Tuesday after Britain shut down flu- shot maker Chiron Corp.'s plant in Liverpool because of manufacturing problems.

California-based Chiron is one of two suppliers of vaccine for the United States. It was supposed to produce up to 48 million doses.

Chiron's problem started in August, when it discovered that 4 million doses were contaminated. Then, less than two weeks ago, top U.S. health officials assured the public that close monitoring of the rest of the supply by the U.S. Food and Drug Administration showed it was fine and that there would be no shortage.

The plant shutdown took U.S. officials by surprise. FDA scientists are going to Britain to discuss ``where the disputes are and how we might be able to reconcile them,'' U.S. Health and Human Services Secretary Tommy Thompson said Wednesday.

He was not optimistic that any of the doses ultimately would be usable.

Vaccine maker Aventis Pasteur is supposed to supply about 54 million doses, but questions remained Wednesday about distribution.

Maxim clinics in groceries and drugstores usually run through mid-November, but this year ``I don't know if we're going to be around that long,'' Wright said.

Although Maxim is reserving flu shots for high-risk groups, it won't vaccinate children under age 9. Younger children need to visit their doctor's offices or a public-health clinic, Wright said.

Elderly patients seeking flu shots jammed Doctor's Walk- In Clinics in Hillsborough and Pinellas counties Wednesday, medical director Stephen Dickey said.

``Our waiting rooms are just unbelievable. It's chaos,'' Dickey said.`

Dickey received a shipment of 3,000 flu-vaccine doses Wednesday but isn't expecting any more. He estimates Doctor's Walk-In clinics will run out by Saturday.

He said the company likely will cancel any work-site clinics scheduled later than Friday.

Baycare Health Systems, which contracts to provide flu shots for companies and their employees, also has canceled clinics at local businesses and shopping malls, spokeswoman Amy Lovett said.

Baycare Health Systems includes hospitals such as St. Joseph's in Tampa and Morton Plant in Clearwater.

Nearly all of its expected flu- shot supply was ordered from Chiron, meaning there aren't doses on hand for Baycare workers who come in contact with chronically ill patients.

``We have some vaccine,'' said Lovett, but Baycare is waiting for guidelines from the Florida Department of Health about how hospitals should distribute flu shots.

Like Baycare, most of the health department's flu shots this year were ordered from Chiron. Many public clinics don't have adult vaccines, but they have doses of children's vaccines made by Aventis.

Pinellas County Health Department spokeswoman Jeannine Mallory said, ``The concern is getting the vaccine out to those who need it the most.''

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

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

Keyword: Flu, to learn how the three types of influenza viruses differ and how the flu is transmitted.

Keyword: Flu, to learn how the three types of influenza viruses differ and how the flu is transmitted. To find a flu-shot clinic, visit the American Lung Association's online guide at www.lungusa.org or Maxim Health System at www.FindaFluShot.com.