I see what you are saying. But if none of the herd is vaccinated, as is becoming the case, a large scale spread of disease could very well occur. I’m talking about the “biggies”...smallpox and polio. As far as mumps, measles, and chickenpox most all of us had those as kids. We lived. But those diseases can sure wreak havoc on adults.
I’m not on board with the flu vaccine. There are too many different strains. There would be no way to make a “mega” vaccine that would cover all of them. Even if there was...the vaccine would probably make a person sicker than the flu would.
the greatest drops of disease occurred from hygiene improvements, public sanitation and water systems, and proper food handling/packaging improvements.