Updated

U.S. health authorities are holding off approval of this year's seasonal flu shot as they probe Australia's ban on the vaccine, which has been found to induce fever in young children, The Australian reported Thursday.

The U.S. Food and Drug Administration (FDA) is collaborating with Australia's Therapeutic Goods Administration (TGA) to "assess any potential implications for the U.S. flu season."

The FDA has also written to Australian pharmaceutical giant CSL — which manufactures the controversial Fluvax vaccine — detailing its "number of significant objectionable conditions" relating to CSL's compliance with American "good manufacturing practice."

FDA investigators observed "deviations" from U.S. manufacturing standards in CSL's production of both seasonal flu and swine flu vaccines for the U.S. market.

The TGA admitted that vials of multi-dose swine flu vaccine Panvax, stockpiled by the Australian federal government, contain the same preservative that is the subject of the FDA's concerns.

"However, there are no related reports of adverse events arising from its use,'' a TGA spokeswoman said. A CSL spokeswoman said discoloration had been noticed in Australian Panvax stocks.

The FDA's director of compliance and biologics quality, Mary Malarkey, issued a scathing assessment after the FDA's annual audit of CSL's Melbourne laboratory in April.

The audit was carried out the week Australian authorities suspended use of the Fluvax vaccine after it triggered febrile fits in nearly one percent of children younger than five.

The FDA's complaints relate to the presence of black particles in multi-dose vials of Afluria, the brand name for CSL's seasonal flu vaccine in the U.S.

The FDA blasted CSL's investigation of the cause as "inadequate."

The TGA spokeswoman said the FDA audit had "nothing to do" with the government's investigation into the children's seasonal flu shot.

It remains suspended for under-fives as researchers struggle to work out why it triggers febrile fits at nine times the usual rate.