You underestimate the ability of diseases to spread. Take Malaria, spread by mosquitos. How are you going to stop them?
Suppose a mosquito drank the blood of an infected person and passing it on to another person 10 miles from point of infection (across the border), or a fly, they feed on feces.
We need to know how it can be passed on as well as what it does not like (a chemical aversion) which could be used to discourage an epidemic.
With people moving around the world as they do today, it's almost impossible to stop the spread of a disease or slow it considerably without a vaccine.
That's the point of the post. Diseases are evolving. Vaccines don't kill all the bugs that infect us, and the ones left behind are resistant to our vaccines, making them harder and harder to control.
That's true, but vaccines are the best we have, so far. Most of them do work and continue to work. Of course there will be failures, but we have to work with what we have. When's the last time you heard of anyone with small pox, diphtheria or even polio? At one time those diseases swept the land in regular epidemics. I remember the polio epidemics very well. Several of my classmates were crippled for life from polio. I, myself had a slight case when I was 2 years old and I suffer today from its after-effects. There have been extremely few cases of polio in the US for years and it is on the verge of being wiped out completely. There is no cure for polio. Vaccine is all we've got.