If you need a photographic image traced into vector, there can be many different ways in which it can be redrawn, depending on what the vector graphic is to be used for.
Below are a few basic types of vector conversion examples. There are other more complex methods of redrawing this graphic which would involve using blends, gradients, gradient meshes and perhaps blur effects. These are mostly raster effects and not 100% vector as the examples below.
Autotracing will usually produce the most realistic results. But then you may as well stick to using the original bitmap image, unless for some reason it needs to be a vector image. The drawback to autotracing a photographic quality image is that it will produce thousands of lines and points, which may cause problems in production.