None of the 5 million or 6 million doses of influenza vaccine made by Chiron Corp. and currently warehoused in the United States has been given to the public, a Food and Drug Administration official said yesterday.

Those lots of vaccine were made at the same Liverpool plant whose output of flu vaccine was blocked from shipment early this week by the British agency that regulates drug manufacturing. The agency took the step because of concerns about the possible contamination of the vaccine during production.

The ban instantly eliminated about 48 million doses of flu vaccine from the U.S. market, which had expected to have about 100 million doses available from all sources this winter.

William Egan of the FDA's Center for Biologics Evaluation and Research said Chiron has not released any of the small amount of its production that was exported late in the summer and stored here. Speaking in a telephone news conference, he said those doses may still be legally under the control of British regulators.

A team from the FDA is scheduled to tour Chiron's Liverpool plant this weekend and to review the findings of Britain's Medicines and Healthcare Products Regulatory Agency.

Egan did not rule out the possibility that the approximately 42 million doses of unshipped Chiron vaccine might eventually be deemed usable, but he said the decision would hinge on more than simply testing samples for contamination.

Some lots checked in August contained a bacterium called serratia.

"One cannot assure the quality of a vaccine or other biological product simply by testing. There are multiple layers of review that must be taken to ensure safety, and testing is only one of them," he said.