European-produced flu vaccine (search) widely used in other countries will be tested at four locations in the United States, the government announced.

The National Institute of Allergy and Infectious Disease is launching the trial in an effort to increase the supply of flu vaccine in this country.

The United States is millions of doses short on flu vaccine this year because of manufacturing problems at a major producer of the vaccine.

NIAID said Thursday it hopes to enroll 1,000 healthy adults in the new tests by Dec. 23 in Rochester, N.Y., Cincinnati, Baltimore and Houston.

While more than 126 million doses of the test vaccine, Fluarix, have been distributed in more than 70 countries worldwide, Fluarix has never been tested or licensed for use in the United States. It is made by GlaxoSmithKline Biologicals of Rixensart, Belgium.

Health and Human Services Secretary Tommy G. Thompson has announced a plan to import 4 million doses of Fluarix as an investigational new drug.

Volunteers who agree to be given Fluarix must first sign an informed consent form acknowledging that they are aware of the potential risks and benefits associated with the investigational vaccine.

"Expanding the number of influenza vaccine sources is critical as we ready ourselves for next year's flu season," said NIAID Director Dr. Anthony S. Fauci.

"Although the vaccine we are testing has a very long safety record in Europe and other parts of the world, the type of study we are conducting must be done before the vaccine can be licensed for use in the United States," added lead investigator Dr. John Treanor of the University of Rochester Medical Center.

In the trial, four out of every five participants will receive Fluarix, while the fifth will receive a placebo. Those receiving placebo vaccine will be offered U.S.-licensed flu vaccine at the conclusion of the monthlong study.

Healthy adults between the ages of 18 and 64 who have not received a flu shot this year are eligible. Participants will visit the clinic twice in the course of the trial.

The trial will be conducted at the University of Rochester Medical Center, Cincinnati Childrens Hospital, University of Maryland School of Medicine and Baylor College of Medicine.