I think I totally agree with you on one thing: that individual's health should not be diagnosed generically. You're totally right, every person has different health needs and webmd does not have the correct answer for why both of our chests may be hurting, for instance. While I think there is a lot that could be improved in the process of vetting for medical school applicants, I fully believe that trained DOs, MDs, NPs, and PAs have the best insight on how each individual person should deal with most common ailments.

I do not profess to be vaccinologist. What I do know about vaccines, in essence has already been highlighted in this post. To go a little deeper, I will say that the theory behind vaccination is that your body will develop immunity to diseases that it encounters. Vaccination uses a damaged, or in the case of smallpox (at least originally), a similar virus to "trick" the body into creating a natural defense against disease.

Why might this not work? Try this terrible metaphor out for size: Imagine a large group of people as a wall into a country. If part of there is a hole in the wall, invaders can get in. Once those invaders get in, they can change their mechanism of attack in the future and then get in though weaker parts of the wall as well as holes. The more places that invaders get in, the better their strategy becomes in the future. This is a very simplified way of explaining how bacterial and viral diseases can adapt to "natural" defenses in larger organisms.