The Middlesex-London Health Unit says the three London, Ont., residents are recovering.
The recall of the burgers began on Wednesday and covers eight-ounce burgers that were sold frozen in packages of six (with a UPC code of 0 55742 37055 3).
The burgers were distributed in Newfoundland and Labrador, Prince Edward Island, Nova Scotia, New Brunswick and Ontario, and sold through Foodland, Sobeys, FreshCo and Price Chopper stores.
Food contaminated with E. coli O157:H7 may not look or smell spoiled but may cause serious and potentially life-threatening illnesses.
Anyone showing signs or symptoms of E. coli O157:H7 infection, in particular stomach pain and severe or bloody diarrhea, should contact their doctor.