Tennessee health officials are working with Pfizer scientists and Centers for Disease Control and Prevention staff to identify whether improperly stored or expired doses of the COVID-19 vaccine were administered in Shelby County.

Tennessee Health Commissioner Lisa Piercey said state officials believe cards with expired vaccine dates were the result of a clerical error at the Shelby County Health Department. However, incomplete vaccine records missing key information, such as temperatures at which vaccine doses were stored, prompted the state to call in experts to help.