There's two types of vaccines. The Astrazeneca and J&J use a virus, and absolutely could produce viral shedding in the traditional sense.

The Pfizer and Moderna vaccines are mRNA vaccines, and it is currently unknown if they can produce shedding.

In theory, anything that stimulates an immune reaction will then stimulate a detox reaction. So if the mRNA vaccines produce an antibody response, then its logical to assume they would produce a detox reaction which could in theory cause the body to reject and "shed" the spike proteins. The immune system serves several functions, its job is to identify, kill, and remove foreign infections. The removal process is the detox process that often results in sweating, defication, urination, etc.

While this is NOT the same as viral shedding, it is still a very real possibility that requires investigation and further medical research. It is entirely within the realm of possibility, and could have implications with unknown consequences.

If people are "detoxing" these spike proteins through their skin, and spreading them then yes, a vaccinated person could spread