Basically, NO, although I often do! If you're going to eat the chicken immediately after sous viding, you don't have to. But an ice bath after sous vide cooking chicken breast is a great idea to stop the cooking process and cool it down quickly if you're going to store it in the fridge to eat later. For a little background... When sous vide cooking first became popular years ago, I would put everything in an ice bath after sous viding it. These days, unless I'm cooking sous vide steak and plan to add MORE heat to it after, like in a mayo seared sous vide ribeye for example, then I don't always pop the food in an ice bath.