1918, a hundred years ago but not that long ago in the scheme of things. Between 3 and 5 % of the world's population died of the flu.
I knew kids who had polio.
Your kids don't need to be infected with cowpox to prevent smallpox because my generation did it and we have the scar on our arm to prove it.
Antibiotics are for secondary infections, viruses don't care .
Chickenpox, let me tell you about shingles. Painful, I get mine on my forehead so everyone can enjoy it.
Could go on and on but you get my drift.