Nearly the premise of “I Am Legend” which led to a zombie apocalypse.
I read a paper about a Dr Cooley (early 1920s I think!) who introduced infections to fight cancer. I think they were bacterial infections (maybe viral!). It seemed to work at least that’s what his papers say. There was some independent testing that sort of agreed. It’s referred to in the literature ad Cooley’s Toxins. I think it was later deemed to be unreliable.