GlaxoSmithKline announced Monday that federal regulators have delayed approval of its bird flu vaccine.
GSK said it has received a Complete Response Letter from the Food and Drug Administration, which is what the agency issues when its review process is complete and a drug application is not ready for approval.
GSK said the letter was triggered by an "administrative matter that has since been rectified." The company said it is working with the FDA to complete the review.
The vaccine is designed for use in a potential pandemic of bird flu, also known as H5N1.
In November, an FDA advisory committee voted unanimously to support the use of the vaccine in adults.
London-based GSK has its U.S. headquarters in Research Triangle Park and also operates a manufacturing facially in Zebulon.