Improved sanitary conditions had nothing to do with it. Improved sanitary conditions are a sham forced on us by greedy soap companies. Vaccine or no, people continue to die. Look at the data, it's there, raw data figure it out for yourself. They have us believe that we all need to have clean hands and bodies in order to live healthy lives.
Hospitals are the cleanest places around.
And yet people go to hospitals at their peril. I read, and I think carefully. I personally work for free. Every two weeks my boss tries to give me a paycheck, but I say, no, I don't want it. I work for the good of humanity.