The U.S. is experiencing a shortage of EpiPens

More than 400 patients in 45 states have reported problems filling their EpiPen subscriptions amid issues with the manufacturing of the automatic injector, Bloomberg reports.

The backdrop: The U.S. Food and Drug Administration warned Meridian Medical Technologies Inc., the unit of Pfizer that manufactures EpiPens, last September about its failures to thoroughly look in to product mishaps, including EpiPen products linked to severe illnesses and patient deaths. A Pfizer spokesman told Bloomberg that a new processes in response the FDA’s warning had caused manufacturing delays.