Vinca minor is a reliable groundcover, especially in shady or partially shady conditions. It is evergreen (though even evergreen plants replace their leaves over time, just not all at once) and fairly deer resistant as well.

If your vinca is losing its leaves, it may have a fungal disease called phomopsis blight caused by Phoma exigua. There are a number of fungal diseases that can affect vinca, but this is the one most likely to kill off only the leafy parts of plants and not affect the roots. You should see small black lesions on the stems where the pathogen entered the plant and then the shoots above that point turn brown or black and fall off. Another very different possibility, is rodent damage. Look around for small holes in the ground. Voles and mice will eat vinca top-growth and spare the root systems.

Courtesy of NYBG Plant Information  Service