This is highly subjective and very much depends on many variables, including what you mean by "systems programming" (more specifically: what level of the stack is your boundary for "system" versus "application").

There is a traditional boundary. System programming is programming at a lower level, code meant for consumption by other software, and never directly used by an end user, while application programming is meant for consumption directly by an end user. Think "game engine's network stack" versus "text editor (that isn't Emacs)".

It's possible to work as a very junior system programmer with no prior programming experience. Everyone has to start somewhere. I've put such people to work doing everything from debugging problems with some data structure implementation to debugging thorny concurrency issues. Generally I take the view that a person is no longer junior when he has had sufficient experience that he can do more than bug fixing in more than one sub-domain of system programming. That wouldn't mean he or she is necessarily senior at that point.