Greetings Frens,
I apologize in advance for so little information, but this is truly the very first time I've heard of this info. A friend of my wife living in Cleveland just posted on FB that she was part of initial testing for a "blind-crossover, four shot program" and is now considered "fully vaccinated." She didn't mention what hospital or company was involved or any other identifiable information. Nothing is popping up on mainstream search engines for me, which conveniently default to vax-a-million bullshit and other noise. I figured I'd pass this new info onto some investigation-hungry Pedes far better suited for the task than myself.
TL;DR: Just heard news of a four shot program in the works to potentially replace the current ones, needs more digging from what little info is available.