It's a leading food safety concern. Robert A. Savage, a food technologist with USDA's Processed Products division, explains the Hotline's verdict. If a product is labeled 'Keep Refrigerated,' that's a warning that not all the bacteria have been inhibited or destroyed. Refrigeration is necessary to keep the food safe to eat. Savage further explains that turkeys and hams and other meats are smoked for flavor, not preservation.
Country hams are different.
With their high salt content and dryness, they are safe at room temperature. Bacteria can't grow on them. This effectively sterilizes them so they are shelf-stable. But some canned hams receive only a mild heat treatment after canning and therefore are not commercially sterile. These hams must be kept refrigerated.