With solid meat products, very light searing takes care of the bacteria clinging to the surface, which is where all the bacteria tend to be. Ground meat, however, will have bacteria throughout.
I really don’t know if immunity to these can be developed. I do miss the steak Tartare mom used to serve, but these days I would have to buy a huge chunk, sear the outside, cut that off and reserve for other meals, and grind the steak myself. I would feel safe doing that. I don’t have a meat grinder or I would be prone to doing that.