The powerful United States Food and Drug Administration has released a warning letter to Australian Biotech giant CSL regarding the companies handling of an internal investigation into flu vaccine problems that affected more than 410 children last spring.

Last April, Australian health authorities were forced to withdraw CSL’s seasonal flu vaccine, Fluvax, from use in children under the age of five after multiple cases of severe vaccine-related febrile reactions in young children were reported.

In April, 23 children from Western Australia alone were admitted to hospitals with convulsions and high fevers after receiving the vaccine.

According to a CSL investigation, the reactions were caused by a single batch of the vaccine.

Although CSL stopped distributing Fluvax and later recalled the vaccine, the Food and Drug Administration still argues that CSL’s internal review was inadequate.

“You failed to thoroughly investigate any unexplained discrepancy, or the failure of a batch or any of its components to meet any of its specifications, and failed to extend the investigation to other batches of the same drug product and other drug products that may have been associated with the specific failure or discrepancy”, said a letter sent from the Food and Drug Administration to CSL Chief Executive Brian McNamee.

CSL responded by stating that they are taking the letter seriously and pointed out that problems with CSL vaccines have not recurred since last April.