I believe the shots were largely an attempt to make the disease evolve to become more deadly. This still may happen, but it seems the shots are too ineffective to keep a person incubating a deadly variant alive.

Another, completely different scenario is we have good intel that germ warfare/biological weapon research has successfully created engineered viruses that utilize the spike protein and attempts to block it and create a framework to rapidly deploy new blocking mechanisms based on mRNA (Operation Warp Speed) were really about preparing for this.