CSL Limited's stock fell sharply by 5.01% during intraday trading on Wednesday, following news that could significantly impact its vaccine business.

The decline comes after the U.S. Defense Secretary announced that the Pentagon will no longer require members of the military to get the flu vaccine, scrapping a public health requirement that had created substantial demand for flu vaccines. CSL Seqirus, a division of CSL Limited, is one of the major flu vaccine manufacturers mentioned in relation to this policy change.

The end of this mandate represents a potential reduction in vaccine sales to the U.S. military, which includes approximately 1.3 million active-duty service members and more than 750,000 additional members of the National Guard and Reserve. This development has raised concerns among investors about future revenue streams for CSL's vaccine division.